阅读说明：本技术 反馈偏置垂直腔面发射激光器 (Feedback bias vertical cavity surface emitting laser ) 是由 佩特·韦斯特伯格 于 2018-11-07 设计创作，主要内容包括：VCSEL可以包括底部DBR反射镜和位于底部DBR反射镜上方的顶部DBR反射镜。VCSEL可以包括位于底部和顶部DBR反射镜的一部分内的垂直光学腔。垂直光学腔可以被配置为发射光信号。该VCSEL可以包括位于底部和顶部DBR反射镜的不同部分内的横向反馈光学腔,其被配置为接收反馈偏置信号,该反馈偏置信号被配置为偏置横向反馈光学腔以调节光信号。该VCSEL可包括形成在底部DBR反射镜和顶部DBR反射镜之间的有源区,该有源区可包括限定氧化物孔隙的氧化层。VCSEL可以包括隔离注入物,该隔离注入物被配置为将垂直光学腔与反馈光学腔电性隔离并且在氧化物孔隙内创建第一孔隙和第二孔隙。(The VCSEL can include a bottom DBR mirror and a top DBR mirror positioned above the bottom DBR mirror. The VCSEL can include vertical optical cavities within a portion of the bottom and top DBR mirrors. The vertical optical cavity may be configured to emit an optical signal. The VCSEL can include lateral feedback optical cavities located within different portions of the bottom and top DBR mirrors configured to receive a feedback bias signal configured to bias the lateral feedback optical cavities to condition the optical signal. The VCSEL can include an active region formed between the bottom DBR mirror and the top DBR mirror, which can include an oxide layer defining an oxide aperture. The VCSEL can include an isolation implant configured to electrically isolate the vertical optical cavity from the feedback optical cavity and create a first aperture and a second aperture within the oxide aperture.)

1. A coupled cavity Vertical Cavity Surface Emitting Laser (VCSEL) comprising:

a bottom Distributed Bragg Reflector (DBR) mirror;

a top DBR mirror formed above the bottom DBR mirror;

a vertical optical cavity within a portion of the bottom DBR mirror and a portion of the top DBR mirror, wherein the vertical optical cavity is configured to emit an optical signal;

a lateral feedback optical cavity located within different portions of the bottom DBR mirror and different portions of the top DBR mirror, wherein the lateral feedback optical cavity is configured to receive a feedback bias signal to bias the lateral feedback optical cavity to condition the optical signal;

an active region formed between the bottom DBR mirror and the top DBR mirror and including an oxide layer defining an oxide aperture; and

an isolation implant formed within the top DBR mirror and configured to electrically isolate the vertical optical cavity from the lateral feedback optical cavity and create a first aperture and a second aperture within the oxide aperture.

2. The coupled cavity VCSEL of claim 1, wherein the isolation implant extends through the top DBR mirror and the active region to at least the bottom DBR mirror.

3. The coupled cavity VCSEL of claim 1, further comprising a bias metal contact formed on a portion of the top DBR mirror, wherein the bias metal contact is configured to receive the feedback bias signal and provide the feedback bias signal to the lateral feedback optical cavity.

4. The coupled cavity VCSEL of claim 1, wherein the feedback bias signal comprises a Direct Current (DC) signal.

5. The coupled cavity VCSEL of claim 1, wherein the feedback bias signal comprises a forward bias signal configured to reduce optical absorption in the transverse feedback optical cavity.

6. The coupled cavity VCSEL of claim 1, wherein the feedback bias signal comprises a reverse bias signal configured to increase optical absorption in the transverse feedback optical cavity.

7. The coupled cavity VCSEL of claim 1, further comprising an anti-reflection layer formed over the top DBR mirror.

8. The coupled cavity VCSEL of claim 1, wherein a width of the oxide aperture is between about 3 microns and about 15 microns.

9. A method of biasing a Vertical Cavity Surface Emitting Laser (VCSEL), the method comprising:

emitting light from an active region of the VCSEL;

passing a first portion of the light through an oxide aperture optically coupled to a vertical optical cavity of the VCSEL;

passing a second portion of the light into a transverse feedback optical cavity of the VCSEL; and

the lateral feedback optical cavity is biased to condition light emitted by the vertical optical cavity.

10. The method of claim 9, wherein the step of biasing the lateral feedback optical cavity to condition light emitted by the vertical optical cavity further comprises biasing the lateral feedback optical cavity with a DC signal.

11. The method of claim 9, further comprising the steps of:

confining the light vertically within the oxide pores; and

the light is laterally confined within the oxide pores.

12. The method of claim 9, further comprising the steps of: adjusting the bias of the transverse feedback optical cavity to a target feedback intensity, wherein the target feedback intensity is associated with both a target three decibel (dB) bandwidth and a target formant of light emitted by the vertical optical cavity.

13. An optical transceiver, comprising:

a bottom Distributed Bragg Reflector (DBR) mirror;

a top DBR mirror positioned above the bottom DBR mirror;

a vertical optical cavity within a portion of the bottom DBR mirror and a portion of the top DBR mirror, wherein the vertical optical cavity is configured to emit an optical signal;

a lateral feedback optical cavity located within different portions of the bottom DBR mirror and different portions of the top DBR mirror, wherein the lateral feedback optical cavity is optically coupled to the vertical optical cavity and configured to receive a feedback bias signal configured to bias the lateral feedback optical cavity to condition the optical signal emitted by the vertical optical cavity;

an active region between the bottom DBR mirror and the top DBR mirror and comprising an oxide layer defining an oxide aperture; and

an isolation implant configured to electrically isolate the vertical optical cavity from the lateral feedback optical cavity and create a first aperture and a second aperture within the oxide aperture.

14. The optical transceiver of claim 13, wherein the isolation implant extends through the top DBR mirror and the active region to at least the bottom DBR mirror.

15. The optical transceiver of claim 13, further comprising a bias metal contact proximate the lateral feedback optical cavity, wherein the bias metal contact is configured to receive the feedback bias signal and provide the feedback bias signal to the lateral feedback optical cavity.

16. The optical transceiver of claim 13, wherein the feedback bias signal comprises a Direct Current (DC) signal.

17. The optical transceiver of claim 13, wherein the feedback bias signal comprises a forward bias signal configured to reduce optical absorption in the lateral feedback optical cavity.

18. The optical transceiver of claim 13, wherein the feedback bias signal comprises a reverse bias signal configured to increase optical absorption in the lateral feedback optical cavity.

19. The optical transceiver of claim 13, wherein the oxide pores are between about 3 microns and about 15 five microns wide.

20. The optical transceiver of claim 13, further comprising an anti-reflective layer proximate the top DBR mirror.

Technical Field

Embodiments discussed herein relate to feedback biased Vertical Cavity Surface Emitting Lasers (VCSELs)

Background

Unless otherwise indicated herein, the material described herein is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.

VCSELs are commonly used in many modern communication components for data transmission. Where the use in data networks is an increasingly common use of VCSELs. VCSELs are used in many optical fiber communication systems to transmit digital data over a network. In one exemplary configuration, the VCSEL can be modulated by digital data to produce an optical signal that includes a bright-dark output period representative of a binary data stream. In actual practice, a VCSEL emits a high optical output representing a binary high and a low optical output representing a binary low. To obtain fast response times, VCSELs are normally bright, but vary from high to low optical output.

The subject matter claimed herein is not limited to implementations that solve any disadvantages noted above or that operate only in environments such as those noted above. Rather, this background is only provided to illustrate one example technology that may practice some embodiments described herein.

Disclosure of Invention

In at least one embodiment, a coupled cavity Vertical Cavity Surface Emitting Laser (VCSEL) may include a bottom Distributed Bragg Reflector (DBR) mirror. The coupled cavity VCSEL can also include a top DBR mirror formed above the bottom DBR mirror. The coupled cavity VCSEL can additionally include a vertical optical cavity within a portion of the bottom DBR mirror and a portion of the top DBR mirror. The vertical optical cavity may be configured to emit an optical signal. The coupled cavity VCSEL can include a lateral feedback optical cavity located in different portions of the bottom DBR mirror and different portions of the top DBR mirror. The lateral feedback optical cavity may be configured to receive a feedback bias signal to bias the lateral feedback optical cavity to condition the optical signal. The coupled cavity VCSEL can also include an active region formed between the bottom DBR mirror and the top DBR mirror. The active region may include an oxide layer defining oxide pores. The coupled cavity VCSEL may additionally include an isolation implant. The isolation implant may be configured to electrically isolate the vertical optical cavity from the lateral feedback optical cavity and create a first aperture and a second aperture within the oxide aperture.

In at least one embodiment, a method of biasing a VCSEL can include emitting light from an active region of the VCSEL. The method may also include passing a first portion of the light through an oxide aperture of a vertical optical cavity optically coupled to the VCSEL. The method may additionally include transmitting a second portion of the light into a lateral feedback optical cavity of the VCSEL. The method may include biasing the lateral feedback optical cavity to condition light emitted by the vertical optical cavity.

In at least one embodiment, the optical transceiver may include a bottom DBR mirror. The optical transceiver may also include a top DBR mirror located above the bottom DBR mirror. The optical transceiver may additionally include a vertical optical cavity within a portion of the bottom DBR mirror and a portion of the top DBR mirror. The vertical optical cavity may be configured to emit an optical signal. The optical transceiver may include a lateral feedback optical cavity located within different portions of the bottom DBR mirror and different portions of the top DBR mirror. The lateral feedback optical cavity is optically coupled to the vertical optical cavity and may be configured to receive a feedback bias signal. The feedback bias signal may be configured to bias the lateral feedback optical cavity to condition the optical signal emitted by the vertical optical cavity. The optical transceiver may also include an active region between the bottom DBR mirror and the top DBR mirror. The active region may include an oxide layer. The oxide layer may define oxide pores. The optical transceiver may additionally include an isolation implant. The isolation implant may be configured to electrically isolate the vertical optical cavity from the lateral feedback optical cavity. The isolation implant may create a first pore and a second pore within the oxide pore.

Drawings

To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only example embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

figure 1 shows a cross-sectional view of an embodiment of a feedback biased VCSEL;

FIG. 2 shows a chip layout of an embodiment of the feedback biased VCSEL of FIG. 1;

FIG. 3 shows a detailed view of the VCSEL mesa of the chip layout of FIG. 2;

FIG. 4 includes a simulated graphical representation of the 3dB bandwidth (gigahertz (GHz)) of an optical signal emitted by the feedback-biased VCSEL of FIG. 1 as a function of feedback intensity;

FIG. 5 includes a simulated graphical representation of the resonance peak (in decibels (dB)) of an optical signal emitted by the feedback biased VCSEL of FIG. 1 as a function of feedback intensity;

FIG. 6 includes a simulated graphical representation of the modulation response of an optical signal emitted by the feedback-biased VCSEL of FIG. 1 as a function of frequency;

FIG. 7 includes a simulated graphical representation of the modulation response of an optical signal emitted by the feedback biased VCSEL of FIG. 1 as a function of frequency; and

figure 8 shows a flow chart of a method of biasing the feedback biased VCSEL of figure 1.

Detailed Description

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, like numerals generally identify like components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein.

One type of laser used in optical data transmission is a Vertical Cavity Surface Emitting Laser (VCSEL). The VCSEL may include a laser cavity sandwiched between and defined by two mirror stacks. VCSELs are typically built on a semiconductor wafer such as gallium arsenide (GaAs). The VCSEL can include a bottom mirror built on a semiconductor wafer. Typically, the bottom mirror comprises a plurality of alternating high and low refractive index layers. When light passes from one refractive index layer to another, a portion of the light is reflected. By using a sufficient number of alternating layers, a high percentage of the light can be reflected by the mirror.

A VCSEL functions, for example, when current is passed through the PN junction to inject carriers into the active region of the VCSEL. Recombination of the injected carriers from the conduction band to the valence band in the VCSEL quantum well produces photons that begin to propagate in the laser cavity. The photons are reflected back and forth. When the bias current is sufficient, optical gain is produced in the active region. When the optical gain equals the cavity loss, lasing occurs, the VCSEL is said to be at threshold bias, and as optically coherent photons are emitted from the top of the VCSEL, the VCSEL begins "excitation".

In general, the present techniques relate to feedback biasing VCSELs (e.g., coupled cavity VCSELs). Using a feedback signal comprising an appropriate feedback strength in combination with an appropriately sized oxide aperture included in the feedback biased VCSEL to bias a portion of the feedback biased VCSEL can improve the modulation response, 3dB bandwidth, and/or formants of the optical signal emitted by the feedback biased VCSEL. Improving the modulation response, 3dB bandwidth, and/or formants of an optical signal as described herein may result in an increase in the modulation speed of the optical signal as compared to the modulation speed of optical signals emitted by other VCSEL technologies (e.g., VCSELs that are not feedback biased by an appropriately sized oxide aperture). Also, the 3dB bandwidth of the optical signal emitted by the feedback biased VCSEL as described herein may not be as much limited by the Relaxation Oscillation Frequency (ROF) as other VCSEL technologies, which may also allow for an increase in the modulation speed of the optical signal to be emitted by the feedback biased VCSEL.

Figure 1 illustrates a cross-sectional view of an embodiment of a feedback biased VCSEL100 (e.g., a coupled cavity VCSEL 100) in accordance with at least one embodiment described herein. The bottom Distributed Bragg Reflector (DBR) mirror 106 may be formed on the bottom contact 136. The active region 104 may be formed on the bottom DBR mirror 106. The top DBR mirror 102 may be formed on the active region 104. The antireflective layer 108 may be formed near, on, and/or over the top DBR mirror 102. In some embodiments, an anti-reflective layer 108 may be formed on the top DBR mirror 102.

An isolation implant 112 may be formed in the top DBR mirror 102 and may extend through to at least a portion of the active region 104. In some embodiments, the isolation implant 112 may extend through the active region 104 so as to contact at least a portion of the bottom DBR mirror 106. A vertical cavity 116 (e.g., a vertical optical cavity) may be formed by the bottom DBR mirror 106 and the top DBR mirror 102. A lateral feedback cavity 118 (e.g., a lateral feedback optical cavity) may also be formed by the bottom DBR mirror 106 and the top DBR mirror 102. A p-type contact metal layer 110 may form an electrical contact on a portion of the top DBR mirror 102. A bias metal contact 114 may form an electrical contact on different portions of the top DBR mirror 102, the bias metal contact 114 being electrically isolated from the p-type contact metal layer 110 by an isolation implant 112. In some embodiments, the bias metal contact 114 may be located near and/or above the lateral feedback cavity 118. The p-type contact metal layer 110 and the bias metal contact 114 may form and/or define an optical aperture 138 on and/or over another different portion of the top DBR mirror 102. The optical aperture 138 may extend over at least a portion of the vertical cavity 116 and the isolation implant 112. The optical aperture 138 may allow light to be emitted by the feedback biased VCSEL100 as an optical signal 142.

The active region 104 may be formed by one or more quantum wells 124, the quantum wells 124 being separated from the oxide layer 126 and the bottom DBR mirror 106 by a plurality of quantum well barriers 141 a-b. The oxide layer 126 may include a vertical cavity oxide aperture 120 defined by an oxidized portion of the oxide layer 126 and the isolation implant 112. Additionally, the oxide layer 126 may include a lateral feedback cavity oxide aperture 122 defined by an oxidized portion of the oxide layer 126 and the isolation implant 112. In some embodiments, the oxide aperture may be defined by a vertical cavity oxide aperture 120 and a lateral feedback cavity oxide aperture 122. For example, in some embodiments, the oxide pores may include both vertical cavity oxide pores 120 and lateral feedback cavity oxide pores 122. Additionally, the oxide pores may define spaces between portions of the oxide layer 126.

During expected operation, the p-type contact metal layer 110 may receive a bias current that may be injected into the quantum well 124. At a sufficiently high bias current, the quantum well 124 may generate light 140a-c and the feedback biased VCSEL100 may begin to "fire" and emit light as an optical signal 142. Light 140a-c emitted by the quantum well 124 may be emitted into the vertical cavity 116 and the lateral feedback cavity 118. Light 140a and 140c emitted into the vertical cavity 116 may be reflected perpendicularly by the various layers included in the vertical cavity 116 toward the optical aperture 138. In addition, a portion of the light 140a and 140c may pass through the vertical cavity oxide aperture 120. Further, a portion of light 140a and 140c may be reflected vertically toward bottom contact 136.

Light 140b coupled into the lateral feedback cavity 118 (e.g., laterally) from the vertical cavity 116 may be reflected by the various layers included in the lateral feedback cavity 118. In addition, the light 140b may be reflected back toward the vertical cavity 116 by the various layers included in the lateral feedback cavity 118. Further, the lateral feedback cavity oxide aperture 122 may allow light 140b reflected back toward the vertical cavity 116 by the layers in the top DBR mirror 102 to enter the bottom DBR mirror 106 and thus the vertical cavity 116. In some embodiments, the bias metal contact 114 may reduce optical losses occurring in the top DBR mirror 102 above the lateral feedback cavity 118 by enhancing reflection and by limiting output losses through the top DBR mirror 102 on which the bias metal contact 114 is formed. The light 140a-c may be reflected through the bottom DBR mirror 106, the top DBR mirror 102, the vertical cavity 116, and the lateral feedback cavity 118 until the light 140a-c is emitted from the optical aperture 138 as the optical signal 142.

In addition, the p-type contact metal layer 110 may receive a Radio Frequency (RF) signal. The RF signal may be modulated onto the optical signal 142 by analog or digital modulation techniques. For example, the RF signal may include a high frequency that may be imposed on the light 140a-c before the light 140a-c is emitted as the optical signal 142. A possible intensity distribution of the optical standing wave can be represented by wave 143.

A Direct Current (DC) feedback bias voltage may be applied to the bias metal contact 114 to adjust the feedback strength of the lateral feedback cavity 118. The formants, modulation response, and/or 3dB bandwidth of the optical signal 142 emitted by the feedback biased VCSEL100 can be adjusted by modifying the DC feedback bias voltage and thereby adjusting the gain/loss of the transverse feedback cavity 118. The DC feedback bias may include a reverse bias signal and/or a forward bias signal. In some embodiments, the reverse bias signal may reduce the feedback intensity by increasing the light absorption within the lateral feedback cavity 118. In these and other embodiments, the forward bias signal may increase the feedback intensity by using gain to compensate for absorption of light 140c in the lateral feedback cavity 118.

A flat modulation response (e.g., low peak of modulation response) of the optical signal 142 emitted by the feedback biased VCSEL100 can be achieved by modifying the DC feedback bias voltage. Adjusting the DC feedback bias voltage such that the feedback biased VCSEL100 emits an optical signal that includes a flat modulation response, a higher 3dB bandwidth, and a lower formant will be discussed in more detail below with reference to figures 4-7.

The feedback strength determined by the geometry of the lateral feedback cavity oxide aperture 122, the DC feedback bias applied to the bias metal contact 114, and the vertical cavity oxide aperture 120 may also improve the modulation response, 3dB bandwidth, and/or formants of the optical signal 142. Improving the modulation response, 3dB bandwidth, and/or formants of the optical signal 142 may increase the modulation speed of the optical signal 142 compared to other VCSEL technologies (e.g., VCSELs that do not implement feedback biasing of the transverse feedback cavity 118 as described herein).

Also, the 3dB bandwidth of the optical signal 142 may not be restricted by the ROF compared to other VCSEL technologies (e.g., VCSELs that do not implement feedback biasing of the transverse feedback cavity 118). Additionally, some embodiments may allow for an increase in the modulation speed of the optical signal 142.

Fig. 2 illustrates a chip layout of an embodiment of the feedback-biased VCSEL100 of fig. 1 in accordance with at least one embodiment described herein. The chip layout may include first and second feedback ground traces 228a, 228b (collectively "feedback ground traces 228"), and first and second optical ground traces 229a, 229b (collectively "optical ground traces 229"). The chip layout may also include feedback signal traces 230a and optical signal traces 230 b. Additionally, the chip layout may include a VCSEL mesa (mesa) 232.

The optical signal trace 230b may be configured to receive a bias current plus an RF signal for injection into the quantum well of the feedback biased VCSEL100, as discussed above with respect to fig. 1. The optical ground trace 229 may be configured to complete a circuit that allows a bias current and/or RF signal to flow through the feedback biased VCSEL 100. Allowing a bias current and/or RF signal to flow or be injected into the quantum well of the biased VCSEL100 can cause the feedback biased VCSEL100 to emit light, as discussed above with respect to figure 1.

The feedback signal trace 230a may be configured to receive a DC feedback bias voltage to adjust the feedback strength of the feedback cavity of the VCSEL100 as discussed above with respect to fig. 1. Additionally, the feedback ground trace 228 may be configured to complete a circuit that allows a DC feedback bias voltage to enter the lateral feedback cavity 118 of the feedback biased VCSEL 100.

The VCSEL mesa 232 can include a number of components configured to bias the lateral feedback cavity 118 and cause the feedback biased VCSEL100 to emit light based on the DC feedback bias voltage, bias current, and RF signal received by the signal trace 230. The VCSEL mesa 232 will be discussed in more detail below in conjunction with figure 3.

Fig. 3 illustrates a detailed view of the VCSEL mesa 232 of the chip layout of fig. 2 in accordance with at least one embodiment described herein. The VCSEL mesa 232 may include a p-type contact metal layer 110, an isolation implant 112, a bias metal contact 114, a vertical cavity oxide aperture 120, and a lateral feedback cavity oxide aperture 122. In some embodiments, the lateral feedback cavity oxide aperture 122 and the vertical cavity oxide aperture 120 may define an oxide aperture. In some embodiments, the oxide pores may be between 3 microns and 15 microns wide. Additionally or alternatively, the width of the oxide pores may be less than 3 microns or greater than 15 microns. Further, the oxide pores may be between 10 and 15 microns in length.

In some embodiments, the VCSEL mesa 232 can include at least one of a first etched trench 334a, a second etched trench 334b, a third etched trench 334c, a fourth etched trench 334d, a fifth etched trench 334e, a sixth etched trench 334f, and a seventh etched trench 334g (collectively "etched trenches 334").

Figure 4 includes a simulated graphical representation 400 of a 3dB bandwidth (in gigahertz (GHz)) of an optical signal emitted by the feedback-biased VCSEL100 of figure 1 as a function of feedback intensity in accordance with at least one embodiment described herein. The feedback strength may be determined according to equation 1.

η x exp (-2 x α L)/sqrt (1- η) formula 1

In equation 1, η may be the fraction of the lasing mode in the VCSEL cavity coupled to the feedback cavity, α may be the loss (per unit of length) in the feedback cavity, and L may be the length of the feedback cavity. In some embodiments, η and L may be determined by the design geometry, and α may be adjusted by the DC feedback bias applied to the lateral feedback cavity (e.g., negative for forward bias, positive for zero bias or reverse bias (e.g., loss)).

Curve 402 represents the 3dB bandwidth of the optical signal as a function of the feedback strength of the feedback DC bias voltage. Circles 404 and 406 represent different sampling bandwidth selections at different feedback strengths.

In the simulation represented in graphical representation 400, the 3dB bandwidths at both circles 404 and 406 are substantially the same or similar. In the simulation, along the curve 402, the 3dB bandwidth of the optical signal at the first point represented by the circle 404 and the 3dB bandwidth of the optical signal at the second point represented by the circle 406 are substantially the same or similar. In the simulation, a first point represented by circle 404 is located at a feedback strength of about 0.16 and a second point represented by circle 406 is located at a feedback strength of about 0.27.

In the simulation, as the feedback strength increases to about 0.22, the 3dB bandwidth increases, at a feedback strength of about 0.22, the 3dB bandwidth drops sharply until a feedback strength of about 0.23 is reached, after which the 3dB bandwidth will start to increase again until a feedback strength of about 0.27 is reached, at a feedback strength of about 0.27, the 3dB bandwidth drops sharply again.

Figure 5 includes a simulated graphical representation 500 of a formant (in decibels (dB)) of an optical signal emitted by the feedback biased VCSEL100 of figure 1 as a function of feedback intensity in accordance with at least one embodiment described herein.

Curve 502 represents the formants of the optical signal as a function of the feedback intensity. Circles 504 and 506 represent different sampling bandwidth selections at different feedback strengths. Circles 504 and 506 may correspond to circles 404 and 406, respectively, discussed above with respect to fig. 4. For example, circles 404 and 504 may both correspond to measurements at a feedback strength of approximately 0.16. Likewise, circles 406 and 506 may both correspond to measurements at a feedback strength of about 0.27.

In the simulation represented in graphical representation 500, although circles 504 and 506 correspond to similar 3dB bandwidths as discussed above with respect to fig. 4, the formants at both circles 504 and 506 may be different. In the simulation, the formant of the optical signal at the first point represented by circle 504 may be approximately equal to 3 dB. In the simulation, the formant of the optical signal at the second point represented by circle 506 may be approximately equal to 20 dB. Thus, biasing the VCSEL with a feedback intensity of about 0.16 may achieve a larger 3dB bandwidth corresponding to a lower formant as compared to biasing the VCSEL with a feedback intensity of about 0.27.

In the simulation, the formants increase as the feedback intensity increases to about 0.22, and at a feedback intensity of about 0.22, the formants decrease sharply until a feedback intensity of about 0.23 is reached, and at a feedback intensity of about 0.23, the formants generally start to increase again until a feedback intensity of about 0.27 is reached, and at a feedback intensity of about 0.27, the formants decrease sharply again. The increased formants may cause a number of errors and/or other problems associated with transmitting data via optical signals. Thus, it may be desirable to operate the feedback biased VCSEL at a lower resonant peak (e.g., at the resonant peak associated with circle 504 in fig. 5). It may also be desirable to operate the feedback biased VCSEL at a higher 3dB bandwidth (e.g., at the 3dB bandwidth associated with circle 404 in fig. 4). By operating the feedback biased VCSEL with a feedback strength of about 0.16, both a lower resonance peak and a higher 3dB bandwidth can be achieved.

Figure 6 includes a simulated graphical representation 600 of a modulation response of an optical signal emitted by the feedback-biased VCSEL100 of figure 1 as a function of frequency in accordance with at least one embodiment described herein.

Curve 602 represents the modulation response of an optical signal as a function of the frequency of the optical signal at a feedback intensity of about 0.16. The circle 604 represents the peak of the modulation response.

In the simulation represented in the graphical representation 600, the modulation response may be relatively flat, meaning that the modulation response may not vary much as the frequency of the optical signal increases and/or decreases. In the simulation, the modulation response at the first point represented by circle 604 may be approximately equal to 4 dB. In simulations, the modulation response may be about 0dB at about 18GHz, and at about 18GHz, the modulation response may increase slightly until about 4dB at about 28GHz is reached. At about 80GHz, the modulation response may be reduced to about-36 dB.

Figure 7 includes a simulated graphical representation 700 of a modulation response of an optical signal emitted by the feedback-biased VCSEL100 of figure 1 as a function of frequency in accordance with at least one embodiment described herein.

Curve 702 represents the modulation response of an optical signal as a function of the frequency of the optical signal at a feedback intensity of about 0.27. The circle 704 represents the peak of the modulation response.

In the simulations represented in graphical representation 700, the modulation response may be relatively steep, meaning that the modulation response may vary significantly as the frequency of the optical signal increases and/or decreases over at least some frequency ranges. In the simulation, the modulation response at the first point represented by circle 704 may be approximately equal to 20 dB. In simulations, the modulation response may be about 0dB at about 18GHz, the modulation response may increase until about 20dB at about 28GHz is reached. At about 80GHz, the modulation response may be reduced to about-36 dB. Thus, biasing the VCSEL with a feedback intensity of about 0.16 may achieve a larger 3dB bandwidth corresponding to a lower formant and flatter modulation response than biasing the VCSEL with a feedback intensity of about 0.27.

Figure 8 illustrates a flow diagram of a method 800 for biasing the feedback biased VCSEL100 of figure 1 in accordance with at least one embodiment described in the present disclosure. The method 800 may be performed in whole or in part by a feedback biased VCSEL (e.g., the feedback biased VCSEL100 of fig. 1). Although represented by discrete blocks, the steps and operations associated with one or more of the blocks of the method 800 may be divided into additional blocks, combined into fewer blocks, or eliminated, depending on the particular implementation.

The method 800 may include block 802, at block 802, light may be emitted from an active region. The active region may be included in a feedback biased VCSEL. In some embodiments, a current may flow through the PN junction to inject carriers into the active region of the feedback biased VCSEL. When the bias current is sufficient, optical gain is generated in the active region, the feedback biased VCSEL can begin to "fire" and light can be emitted by the vertical cavity (e.g., vertical optical cavity), as discussed above.

At block 804, a first portion of the light may pass through an oxide aperture optically coupled to the vertical cavity. Alternatively or additionally, oxide voids may be included in the vertical cavity, and/or the vertical cavity may be at least partially formed and/or defined. The oxide pores may be defined by an oxide layer comprising one or more oxidized regions and one or more non-oxidized regions. As disclosed, for example, in fig. 1-9, the isolation implant may divide the oxide pore into two separate pores. For example, the oxide pores may include a vertical cavity oxide pore and a lateral feedback cavity oxide pore separated by a spacer implant.

At block 806, a second portion of the light may enter the lateral feedback cavity. A second portion of the light may be reflected by the layers included in the lateral feedback cavity towards the vertical cavity.

At block 808, the lateral feedback cavity may be biased to condition light emitted by the vertical cavity. In some embodiments, biasing the lateral feedback cavity may adjust the gain or loss of the lateral feedback cavity. For example, reverse biasing the lateral feedback cavity may increase light absorption within the lateral feedback cavity. As another example, forward biasing the lateral feedback cavity may reduce light absorption within the lateral feedback cavity.

In some embodiments, the method 800 may include additional operations. For example, the method 800 may also include biasing the lateral feedback cavity using the target feedback strength. Alternatively or additionally, the target feedback strength may be determined as a target feedback strength associated with both the target 3dB bandwidth and the target formant. The target feedback strength may be calculated according to equation 1. Alternatively or additionally, the target feedback intensity may be at least 0.05, at least 0.1, or at least 0.15, such as 0.16 or about 0.16 (e.g., 0.16 ± 10% or 20%). The target 3dB bandwidth may be at least 25GHz or at least 30GHz, for example 32.5GHz or about 32.5 GHz. The target formant may be less than 10dB or less than 5dB, such as 3dB or about 3 dB. In some embodiments, the feedback strength, 3dB bandwidth, and/or formants may be measured and/or estimated during operation, and may be adjusted up or down until one or more of the measured or estimated values are equal to or approximately equal to the respective targets.

Modifications, additions, or omissions may be made to method 800 without departing from the scope of the disclosure. For example, the operations of method 800 may be performed in a different order. Additionally or alternatively, two or more operations may be performed simultaneously. Further, the outlined operations and actions are only provided as examples, and some of the operations and actions may be optional, may be combined into fewer operations and actions, or may be expanded into additional operations and actions without departing from the essence of the disclosed embodiments.

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate and/or applicable. Various singular/plural permutations may be expressly set forth herein for the sake of clarity.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. Moreover, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, refers to at least two recitations, or two or more recitations.) furthermore, in those instances where a convention (convention) similar to "A, B and at least one of C, etc." is used, it is typically the intent of such construction that one skilled in the art will appreciate the meaning of such a convention (e.g., "a system having at least one of A, B and C" will include, but not be limited to, systems having only A, only B, only C, A + B, A + C, B + C, and/or A + B + C, etc.). in those instances where a convention similar to "at least one of A, B or C, etc." is used, in general, it is intended that such structures be understood by those skilled in the art to have the meaning stated (e.g., "a system having at least one of A, B or C" would include, but not be limited to, systems having only a, only B, only C, A + B, A + C, B + C, and/or a + B + C, etc.). It will also be understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "a or B" should be understood to include the possibility of "a" or "B" or "a and B".

Further, when features or aspects of the disclosure are described in terms of markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the markush group.

As will be understood by those skilled in the art, for any and all purposes, such as in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily identified as being fully descriptive and having the same range broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein may be readily broken down into a lower third, a middle third, an upper third, and so on. As one of ordinary skill in the art will also appreciate, all languages such as "up to," "at least," and the like include the recited quantities and refer to ranges that may be subsequently broken down into sub-ranges as discussed above. Finally, as will be understood by those skilled in the art, a range includes each individual member. Thus, for example, a group having 1-3 cells refers to a group having 1, 2, or 3 cells. Similarly, a group having 1-5 cells refers to groups having 1, 2, 3, 4, or 5 cells, and so forth.

From the foregoing, it will be appreciated that various embodiments of the disclosure have been described herein for purposes of illustration, and that various modifications may be made without deviating from the scope and spirit of the disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the following claims. The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.