CN102738693A - Waveguide mode-locked laser - Google Patents

Abstract

The present invention proposes a waveguide mode-locked laser, which includes a semiconductor saturable absorbing mirror, a waveguide gain medium, a waveguide grating and a pumping source. The source is set on the waveguide grating. The waveguide mode-locked laser of the present invention adopts special means to fix the semiconductor saturable absorbing mirror at one end of the gain medium as a cavity mirror in the laser cavity. In addition, a femtosecond micromachining system is used for Write the grating into the waveguide channel point-to-point on the doped substrate, and use the dispersion compensation of the grating and the characteristics of the saturable absorbing mirror of the semiconductor to realize passive mode locking.

Description

Waveguide mode-locked lasers

technical field

The invention relates to the field of laser technology, in particular to a picosecond passive mode-locked laser based on a full waveguide structure in which the waveguide is the gain medium.

Background technique

With the development of laser technology and optical waveguide technology, the development of integrated optics has been effectively promoted, and a certain foundation has been laid for the production of optical integrated chips. Due to its poor stability, the light source is difficult to couple with the optical fiber. The optical fiber source is relatively large in the optical integrated device, and it is difficult to adapt to the development of optical integrated devices, let alone the production of optical integrated chips. In 2002, J.R.Lee's research group pumped the Nd:YAG gain medium with a length of 60 mm, a width of 11 mm and a thickness of 200 μm by using a semiconductor laser array to obtain an output of 150 W. signal light, the light-to-light conversion rate reaches 35%. At the same time, through the positive confocal unstable cavity, the output brightness is increased by 26 times, and the power is only reduced by 12%. In China, Zhang Xiaoxia and others conducted research on optical waveguide lasers and amplifiers (patent publication number: 1752778).

The advantage of waveguide mode-locked lasers is that they are highly integrated, which will effectively promote the development of optical integration technology. Unfortunately, the current ultra-short and ultra-fast mode-locked lasers, in addition to the development of circular waveguides such as optical fibers, the current waveguide lasers exist There are many problems with discrete components. For example, only waveguide devices are used as gain media in waveguide lasers, while external solid or fiber devices are used for pumping and other devices, which greatly reduces the high integration of waveguide mode-locked lasers. , It also sets obstacles for the development of optical integration technology.

Contents of the invention

In order to solve the technical problems in the background technology, the present invention proposes a waveguide mode-locked laser. A semiconductor saturable absorbing mirror is fixed by special means at one end of the gain medium as a cavity mirror in the laser cavity. The second micromachining system writes the grating into the waveguide channel point-to-point on the doped substrate, and uses the dispersion compensation of the grating and the characteristics of the saturable absorbing mirror of the semiconductor to realize passive mode locking.

The technical solution of the present invention is: a waveguide mode-locked laser, characterized in that: the laser includes a semiconductor saturable absorbing mirror, a waveguide gain medium, a waveguide grating and a pump source, and the semiconductor saturable absorbing mirror and the waveguide grating are respectively It is arranged at both ends of the waveguide gain medium, and the pumping source is arranged on the waveguide grating.

The above-mentioned waveguide gain medium includes an undoped substrate and a gain material doped on the substrate.

The above-mentioned waveguide gain medium is a femtosecond laser nonlinearly induced refractive index change in the femtosecond processing system to produce a laser gain waveguide. The femtosecond laser passes through the slit system for beam shaping and microscopic objective lens focusing to generate refraction inside the doped material The gain waveguide formed by increasing the rate.

The above-mentioned waveguide grating is a waveguide grating fabricated point-to-point on a crystal substrate with a Brewster angle in a femtosecond processing system, and the waveguide grating performs dispersion compensation for the entire system.

The above-mentioned pumping source is a semiconductor laser array composed of 8 laser diodes.

Above-mentioned semiconductor laser array comprises semiconductor laser diode carrier (41), laser diode (42), the reflective film (43) of band slit and the high reflection film of 98%; Described semiconductor laser diode carrier is a plurality of, and described laser diode The semiconductor laser diode carriers are arranged in the semiconductor laser diode carrier, corresponding to the semiconductor laser diode carriers one by one, and the plurality of semiconductor laser diode carriers are arranged on the reflective film with slits.

The gain material mentioned above is a gain material doped with rare earth elements or doped with ytterbium.

The above-mentioned waveguide gain medium has a thickness of 220 μm, a width of 11 mm, and a length of 60 mm.

The aforementioned semiconductor saturable absorption reflector is fixed at the output end of the gain medium through a precision control platform.

The invention provides a highly integrated passive mode-locked solid planar waveguide laser development method, which provides a highly integrated waveguide light source for waveguide mode-locked lasers in the field of optical integration;

The present invention mainly considers the highly integrated problem of waveguide mode-locked lasers, and additionally solves the increase of diffraction loss caused by the thickness of the working material (generally in the order of 100 μm), by directly growing a semiconductor on the end face of the gain medium. The saturable absorber and the addition of a waveguide grating of the same size on the other end face reduce diffraction loss and improve integration.

Description of drawings

Fig. 1 is the overall structure schematic diagram of the waveguide mode-locked laser of the present invention;

Fig. 2 is the schematic diagram of the pumping structure of the waveguide mode-locked laser of the present invention;

Fig. 3 is a schematic diagram of the resonant cavity structure of the waveguide mode-locked laser of the present invention;

Detailed ways

Referring to Fig. 1, the waveguide mode-locked laser of the present invention is mainly composed of 4 parts, a semiconductor saturable absorbing mirror 1, a waveguide gain medium 2, a waveguide grating 3, a laser diode array pump source 4; a semiconductor saturable absorbing mirror 1 The waveguide grating and the waveguide grating 3 are arranged at both ends of the waveguide gain medium 2, and the laser diode array pump source 4 is arranged on the waveguide grating. The semiconductor saturable absorbing mirror 1 is fixed to the output end of the waveguide gain medium 2 through a precision control platform, and the semiconductor saturable absorbing mirror 1 is fixed with special glue, thereby realizing the saturable absorbing mirror 1 It is integrated with the waveguide to meet the structure of the whole waveguide.

Referring to Fig. 2 and Fig. 3, the waveguide gain medium 2 is a doped material with a thickness of 220 μm, a width of 11 mm, and a length of 60 mm. The bottom is an undoped base 22, and the upper part is a doped gain material 21. In the femtosecond processing system, the femtosecond laser is used to induce the change of the refractive index nonlinearly to generate a laser gain waveguide. The femtosecond laser passes through the slit system for beam shaping and the microscopic objective lens focuses to generate an increase in the refractive index inside the doped material, thereby forming a gain. Waveguide, processing of the processing system yielded the waveguide gain medium shown in Figure 3.

Referring to Figure 3, the waveguide grating 3 is a waveguide grating 32 fabricated point-to-point on a crystal substrate 31 with a Brewster angle by using a femtosecond laser technician system. The dispersion and bandwidth of this grating are strictly calculated to compensate for the dispersion of the entire system .

Referring to Fig. 2, the pumping source 4 is a semiconductor laser array composed of 8 laser diodes, which is used to pump the waveguide gain medium. , a laser diode 42, a reflective film 43 with a slit and a 98% high reflective film 44. Since the waveguide is relatively thin, generally 200-400 μm, the utilization rate of the single-pass pump light for the gain medium is relatively low. In order to solve the problem, a 98% high-reflection film is coated on the bottom of the gain medium. In this way, the purpose of two-way absorption is achieved, and the absorption capacity of pump light is improved.

Claims (10)

1. waveguide mode-locked laser, it is characterized in that: described laser comprises semiconductor saturable absorption reflector, waveguide gain medium, waveguide grating and pumping source, described semiconductor saturable absorption mirror and waveguide grating are respectively located at waveguide gain medium At both ends, the pumping source is arranged on the waveguide grating. 2 . The waveguide mode-locked laser according to claim 1 , characterized in that: the waveguide gain medium comprises a solid material of laser glass or laser crystal doped with rare earth elements. 3. The waveguide mode-locked laser according to claim 2, characterized in that: the gain waveguide is a femtosecond laser nonlinearly induced refractive index change in the femtosecond processing system to generate a laser gain waveguide, and the femtosecond laser passes through the slit The beam shaping of the system and the focusing of the microscopic objective create a gain waveguide with an increased refractive index inside the doped material. 4. The waveguide mode-locked laser according to claim 2, characterized in that: the gain waveguide can be a waveguide structure fabricated inside or on the surface of the laser medium by ion implantation, ion exchange, or photolithography. 5. The waveguide mode-locked laser according to claim 3, characterized in that: the waveguide grating is a waveguide grating made point-to-point on a crystal substrate with a Brewster angle in a femtosecond processing system, and the waveguide grating Dispersion compensation is performed on the entire system. 6. The waveguide mode-locked laser according to claim 1, wherein the grating is a chirped fiber grating connected to the gain waveguide, or a chirped mirror. 7. The waveguide mode-locked laser according to claim 5, wherein: the semiconductor laser array comprises a semiconductor laser diode carrier, a laser diode, a reflective film with a slit and a 98% high reflective film; the semiconductor laser There are multiple diode carriers, and the laser diodes are arranged in the semiconductor laser diode carrier in one-to-one correspondence with the semiconductor laser diode carriers, and the plurality of semiconductor laser diode carriers are arranged on the reflective film with slits. 8. The waveguide mode-locked laser according to any one of claims 2-6, wherein the gain material is a gain material doped with ytterbium, doped with erbium, doped with holmium, doped with thulium or doped with yttrium. 9. The waveguide mode-locked laser according to claim 7, characterized in that: the diameter of the gain waveguide is 0.5 μm-200 μm, and the gain waveguide is a single-mode or multi-mode waveguide. 10. The waveguide mode-locked laser according to claim 8, characterized in that: the semiconductor saturable absorbing mirror is fixed on the output end of the gain medium or within one millimeter from the side of the waveguide through a precision control platform; The saturable absorption mirror is a semiconductor saturable absorption mirror or a carbon nanotube.

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