阅读说明：本技术 一种能提高飞秒脉冲重复率的8字型主副腔结构激光器 (8-shaped main and auxiliary cavity structure laser capable of improving femtosecond pulse repetition rate ) 是由 杨中民 乔田 韦小明 林巍 于 2020-06-30 设计创作，主要内容包括：本发明公开了一种能提高飞秒脉冲重复率的8字型主副腔结构激光器。所述激光器包括了波分复用器、1×2耦合器、2×2耦合器、第一偏振控制器、第二偏振控制器、隔离器和增益光纤。本发明与普通的线性腔锁模激光器不同,使用了镀弱反射二色膜的高掺杂特殊增益光纤,构成了弱调制F-P腔,具有独特的输出特性。本发明使用被动锁模,与现有的主动锁模激光器相比,激光器结构简单,短小精悍,容易实现重复频率高于100 MHz的脉冲输出,在高重复率领域有着广泛的应用。(The invention discloses an 8-shaped main cavity structure laser and an 8-shaped auxiliary cavity structure laser capable of improving the repetition rate of femtosecond pulses. The laser comprises a wavelength division multiplexer, a 1 x 2 coupler, a 2 x 2 coupler, a first polarization controller, a second polarization controller, an isolator and a gain fiber. Different from a common linear cavity mode-locked laser, the invention uses the high-doped special gain optical fiber plated with the weak reflection bicolor film to form a weak modulation F-P cavity, and has unique output characteristic. Compared with the existing active mode-locked laser, the passive mode-locked laser has the advantages of simple structure, short and exquisite structure, easy realization of pulse output with the repetition frequency higher than 100 MHz, and wide application in the field of high repetition rate.)

1. An 8-shaped main cavity structure laser capable of improving the femtosecond pulse repetition rate is characterized by comprising a Wavelength Division Multiplexer (WDM) (1), a 1 x 2 coupler (5), a 2 x 2 coupler (4), a first Polarization Controller (PC) (2-1), a second Polarization Controller (PC) (2-2), an isolator (6) and a gain fiber (7);

two ends of a Wavelength Division Multiplexer (WDM) (1) are respectively connected with two interfaces at one end of a 2 x 2 coupler (4); the isolator (6) and the 1 multiplied by 2 coupler (5) are sequentially connected with the other end of the 2 multiplied by 2 coupler (4); the gain fiber (7) is connected between the 2 x 2 couplers (4) of the Wavelength Division Multiplexer (WDM) (1) or between the isolator (6) and the 2 x 2 couplers (4); when the gain fiber (7) is connected into the light path, a weak modulation F-P cavity is formed; the first Polarization Controller (PC) (2-1) and the second Polarization Controller (PC) (2-2) are respectively clamped at any position at two ends of the 2 x 2 coupler (4); when the gain fiber (7) is connected into a light path, a weak modulation F-P cavity is formed, the modulation effect of the weak modulation F-P cavity enables mode locking pulses to present a unique comb shape in a time domain, the effect of doubling the repetition frequency of output pulses is achieved, pulse pumping light is input from the pumping end of a Wavelength Division Multiplexer (WDM) (1), pulse signal light is output from the output end of a 1 x 2 coupler (5), and the 8-shaped main cavity structure laser capable of improving the repetition rate of femtosecond pulses is realized.

2. The 8-shaped main cavity structure laser capable of improving the repetition rate of femtosecond pulses according to claim 1, wherein when the gain fiber (7) is connected between the Wavelength Division Multiplexer (WDM) (1) and the 2 x 2 coupler (4), one end of the Wavelength Division Multiplexer (WDM) (1), the gain fiber (7) and the 2 x 2 coupler (4) forms a nonlinear amplification ring mirror, and the other end of the isolator (6), the 1 x 2 coupler and the 2 x 2 coupler (4) forms a nonlinear ring mirror.

3. The 8-shaped main and auxiliary cavity structure laser capable of improving the repetition rate of femtosecond pulses according to claim 1, wherein when the gain fiber (7) is connected between the isolator (6) and the 2 x 2 coupler (4), one ends of the Wavelength Division Multiplexer (WDM) (1) and the 2 x 2 coupler (4) form a nonlinear ring mirror, and the other ends of the gain fiber (7), the isolator (6), the 1 x 2 coupler (5) and the 2 x 2 coupler (4) form a mirror.

4. The 8-shaped main cavity and auxiliary cavity structure laser capable of improving the repetition rate of femtosecond pulses is characterized in that two ends of the gain fiber (7) are plated with dichroic films with weak reflection to signal light after mirror polishing treatment, the dichroic films are connected into an optical path in a glue bonding or sleeve connection mode, the dichroic films have weak reflection to the signal light, the gain fiber (7) forms an F-P auxiliary cavity in the cavity, and the F-P auxiliary cavity is a weak modulation F-P cavity; the reflectivity of two ends of the weak modulation F-P cavity to signal light is less than 30%; the fundamental frequency repetition rate of the mode locking pulse is larger than 50 MHz, and the repetition frequency of the comb-shaped pulse comb teeth at the output end is larger than 500 MHz after the weak modulation F-P cavity is doubled.

5. The 8-shaped main cavity structure laser capable of improving the repetition rate of femtosecond pulses according to the claim 4, wherein after all the components are connected, the position of the gain fiber (7) needs to be adjusted until the loss in the mode-locked resonant cavity is minimum; the gain fiber (7) is placed in a glass tube or a ceramic tube; after the position of the gain fiber (7) is determined, the joint of the glass tube or the ceramic tube is fixed by using a glue bonding or sleeve connection mode.

6. The 8-shaped main-auxiliary cavity structure laser capable of improving the repetition rate of femtosecond pulses according to claim 1, wherein the gain fiber (7) is a high-concentration doped luminescent ion fiber, the luminescent ions of the high-concentration doped luminescent ion fiber are combinations of one or more of lanthanide ions and transition metal ions, and the gain per unit length of the gain fiber (7) is greater than 0.5 dB/cm.

Technical Field

The invention relates to the field of ultrafast lasers, in particular to an 8-shaped main cavity and auxiliary cavity structure laser capable of improving the repetition rate of femtosecond pulses.

Background

The mode-locked laser has inherent advantages in the directions of optical frequency calibration, ultra-fast measurement and the like because the output pulse of the mode-locked laser has a locked phase relationship among longitudinal modes, and is one of the hotspots of research. Taking thulium-doped mode-locked fiber laser as an example, because thulium ions cover a large number of 'fingerprint regions' of atmospheric molecules at a broadband gain of 1.8-2.1 μm, the thulium-doped mode-locked fiber laser is applied to high-sensitivity gas detection. In addition, the femtosecond ultrashort pulse generated by the mode-locked fiber laser with high fundamental frequency repetition rate also has wide application in the aspects of fiber communication, material processing, medical treatment and the like.

Mode-locked lasers can be roughly classified into active mode-locked lasers and passive mode-locked lasers according to different mode-locking modes. The active mode-locked laser maintains the locking of the phase relation by an external active modulation device (such as an acousto-optic modulator); the passive mode-locked laser utilizes the saturable absorption effect, and adds a saturable absorber or an equivalent saturable absorber in the laser cavity to enable light to spontaneously form phase locking in the process of oscillating in the laser cavity. Different from the active mode-locked laser with high cost and complex laser structure, the passive mode-locked laser does not need additional modulation, can realize a simple and compact structure, and can more easily realize the pulse output with high repetition rate.

The invention provides an 8-shaped main cavity structure laser and an 8-shaped auxiliary cavity structure laser capable of improving the femtosecond pulse repetition rate based on a high-concentration doped luminescent ion optical fiber on the basis of an original passive 8-shaped cavity mode-locked laser. The secondary cavity is formed by a weakly modulated F-P cavity. Under the action of weak modulation, the mode-locking pulse is controlled, and a unique comb shape is presented in the time domain. The interval between the comb teeth is constant, the length of the F-P cavity is properly reduced, the repetition frequency can easily reach GHz level, and the method has wide application prospect in the field of high repetition rate and the research aspect of pulse theory.

Disclosure of Invention

The invention aims to provide an 8-shaped main cavity structure laser and an 8-shaped auxiliary cavity structure laser capable of improving the femtosecond pulse repetition rate. The secondary cavity is formed by a weakly modulated F-P cavity. Under the action of the weak modulation F-P cavity, the mode locking pulse is controlled to present a unique comb shape on the time domain of the output pulse.

The second purpose of the invention is to provide a design idea and a design scheme for constructing an 8-shaped main and auxiliary cavity structure laser capable of improving the femtosecond pulse repetition rate.

The invention also aims to provide application of the linear cavity mode-locked fiber laser containing the weak modulation auxiliary cavity.

The purpose of the invention is realized by at least one of the following technical solutions.

An 8-shaped main cavity structure laser capable of improving the repetition rate of femtosecond pulses comprises a Wavelength Division Multiplexer (WDM), a 1 x 2 coupler, a 2 x 2 coupler, a first Polarization Controller (PC), a second Polarization Controller (PC), an isolator and a gain fiber;

two ends of a Wavelength Division Multiplexer (WDM) are respectively connected with two interfaces at one end of the 2 multiplied by 2 coupler; the isolator and the 1 multiplied by 2 coupler are sequentially connected to the other end of the 2 multiplied by 2 coupler; gain fiber access between 2 x 2 couplers or between an isolator and a 2 x 2 coupler of a Wavelength Division Multiplexer (WDM); when the gain optical fiber is connected into the optical path, a weak modulation F-P cavity is formed; the first Polarization Controller (PC) and the second Polarization Controller (PC) are respectively clamped at any positions at two ends of the 2 multiplied by 2 coupler; when the gain fiber is connected into the optical path, a weak modulation F-P cavity is formed, the modulation effect of the weak modulation F-P cavity enables mode locking pulses to present a unique comb shape in a time domain, and the effect of doubling the repetition frequency of output pulses is achieved.

Further, when the gain fiber is accessed between the Wavelength Division Multiplexer (WDM) and the 2 × 2 coupler, one end of the Wavelength Division Multiplexer (WDM), the gain fiber and the 2 × 2 coupler forms a nonlinear amplification ring mirror, and the other end of the isolator, the 1 × 2 coupler and the 2 × 2 coupler forms a nonlinear ring mirror.

Further, when the gain fiber is connected between the isolator and the 2 × 2 coupler, one ends of a Wavelength Division Multiplexer (WDM) and the 2 × 2 coupler form a nonlinear ring mirror, and the other ends of the gain fiber, the isolator, the 1 × 2 coupler, and the 2 × 2 coupler form a mirror.

Further, after mirror polishing is carried out on two ends of the gain optical fiber, a dichroic film with weak reflection to signal light is plated, the dichroic film is connected into a light path in a glue bonding or casing connection mode, the dichroic film has weak reflection to the signal light, the gain optical fiber forms an F-P auxiliary cavity in the cavity, and the F-P auxiliary cavity is a weak modulation F-P cavity; the reflectivity of two ends of the weak modulation F-P cavity to signal light is less than 30%; the fundamental frequency repetition rate of the mode locking pulse is larger than 50 MHz, and the repetition frequency of the comb-shaped pulse comb teeth at the output end is larger than 500 MHz after the weak modulation F-P cavity is doubled.

Furthermore, after all the components are connected, the position of the gain fiber needs to be adjusted until the loss in the mode-locked resonant cavity is minimum; the gain optical fiber is placed in a glass tube or a ceramic tube; after the position of the gain optical fiber is determined, the joint of the glass tube or the ceramic tube is fixed by using a glue bonding or sleeve connection mode.

Furthermore, the gain optical fiber is a high-concentration doped luminescent ion optical fiber, luminescent ions of the high-concentration doped luminescent ion optical fiber are one or a combination of lanthanide ions and transition metal ions, and the unit length gain of the gain optical fiber is greater than 0.5 dB/cm.

Compared with the prior art, the invention has the following advantages:

the invention provides an 8-shaped main cavity structure laser and an 8-shaped auxiliary cavity structure laser capable of improving the repetition rate of femtosecond pulses. Different from the common linear cavity mode-locked laser, the invention uses the high-doped special gain fiber plated with the weak-reflection bicolor film to form a weak-modulation F-P cavity, and has unique output characteristic.

Compared with the existing active mode-locked laser, the passive mode-locked laser has the advantages of simple structure, short and exquisite structure, easy realization of pulse output with the repetition frequency higher than 100 MHz, and wide application in the field of high repetition rate.

The invention can adopt the forms of plasma sputtering coating and the like to coat the dichroic mirror on the end surface of the optical fiber, combines the technologies of sleeve bonding and the like, can realize full optical fiber of the laser, has higher environmental stability and is less interfered by the outside.

The invention has the advantages of small and light integral structure, convenient carrying after packaging and wide application prospect.

Drawings

FIG. 1 is a structural diagram of an 8-shaped primary and secondary cavity structured laser capable of increasing the repetition rate of femtosecond pulses according to embodiment 1 of the present invention;

fig. 2 is a structural diagram of a mode-locked laser with an 8-shaped cavity main and auxiliary cavity structure in embodiment 2 of the present invention;

FIG. 3 is a graph showing the simulation result of the output pulse sequence in test example 1 of the present invention;

FIG. 4 is a graph showing the simulation results of a single pulse in test example 1 of the present invention;

FIG. 5 is a graph showing the results of radio frequency spectrum simulation in test example 1 of the present invention;

FIG. 6 is a graph showing the results of a spectrum simulation in test example 1 of the present invention;

FIG. 7 is a graph showing the simulation result of the output pulse sequence in test example 2 of the present invention;

FIG. 8 is a graph showing the simulation results of a single pulse in test example 2 of the present invention;

FIG. 9 is a graph showing the results of radio frequency spectrum simulation of test example 2 of the present invention;

FIG. 10 is a graph showing the results of the spectral simulation of test example 2 of the present invention.

Detailed Description

The following detailed description of embodiments of the invention is provided in connection with the accompanying drawings. But the embodiments of the present invention are not limited thereto.