CN-122026230-A - Novel open-loop external cavity spectrum beam combining device of semiconductor laser

CN122026230ACN 122026230 ACN122026230 ACN 122026230ACN-122026230-A

Abstract

The invention discloses a novel open-loop external cavity spectrum beam combining device of a semiconductor laser, which comprises the semiconductor laser, a fast axis collimating mirror, a beam rotating element, a slow axis collimating mirror, a first cylindrical surface transmission lens, a transmission grating, a second cylindrical surface transmission lens, a quarter wave plate and a first total reflection mirror which are sequentially arranged along an output optical axis of the semiconductor laser, wherein a second total reflection mirror is vertically arranged in a-1-order diffraction direction of the transmission grating, the polarization direction of the highest diffraction efficiency of the transmission grating is mutually perpendicular to the polarization direction of an output beam of the semiconductor laser, when the light beam transmitted along a 0-order diffraction direction of the transmission grating is reflected back to the transmission grating through the first total reflection mirror, the polarization direction of the light beam is consistent with the polarization direction of the highest diffraction efficiency of the transmission grating, and the-1-order diffraction light beam of the transmission grating is reflected through the second total reflection mirror and then returns to the semiconductor laser as a feedback light beam to form wavelength locking. The spectrum beam combining device disclosed by the invention has the advantages of easiness in realizing wavelength locking and high beam combining efficiency.

Inventors

JIANG MENGHUA
WANG XIAOTIAN
QIN WENBIN
CAO YINHUA
LIU YOUQIANG

Assignees

北京工业大学

Dates

Publication Date: 20260512
Application Date: 20260212

Claims (9)

1. The novel open-loop external cavity spectrum beam combining device of the semiconductor laser is characterized by comprising the semiconductor laser, a fast axis collimating mirror, a light beam rotating element, a slow axis collimating mirror, a first cylindrical surface transmission lens, a transmission grating, a second cylindrical surface transmission lens, a quarter wave plate and a first total reflecting mirror which are sequentially arranged along an output optical axis of the semiconductor laser, wherein a second total reflecting mirror is vertically arranged in a-1-order diffraction direction of the transmission grating; the polarization direction of the light beam transmitted along the 0-order diffraction direction of the transmission grating is consistent with the polarization direction of the transmission grating with highest diffraction efficiency when the light beam is reflected back to the transmission grating through the first total reflection mirror by the quarter wave plate, and the-1-order diffraction light beam of the transmission grating is reflected by the second total reflection mirror and then returns to the semiconductor laser as a feedback light beam to form wavelength locking.
2. The spectral beam combining device as claimed in claim 1, wherein the output beam of the spectral beam combining device is mainly composed of three parts, the first part is laser light which is output by the semiconductor laser after being diffracted by the transmission grating-1 order and reflected back by the second total reflection mirror to the transmission grating and output along the grating transmission direction, the second part is laser light which is output by the semiconductor laser after being transmitted along the 0-order diffraction direction of the transmission grating and reflected back to the transmission grating by the second cylindrical transmission lens, the quarter wave plate and the first total reflection mirror and output along the 1-order diffraction direction of the transmission grating, and the third part is laser light which is output by the semiconductor laser after being diffracted by the transmission grating 1-order.
3. The optical spectrum combining apparatus of claim 1 wherein the semiconductor laser is disposed on a front focal plane of the first cylindrical transmission lens, the transmission grating is disposed on a rear focal plane of the first cylindrical transmission lens and on a front focal plane of the second cylindrical transmission lens, the first total reflection mirror is disposed on a rear focal plane of the second cylindrical transmission lens, and the first total reflection mirror and the second total reflection mirror totally reflect the light beam incident thereon along an original optical path.
4. The spectral beam combining device of claim 1, wherein the front facet of the semiconductor laser is coated with an anti-reflection film having a transmittance of 99% or more.
5. The device for combining light spectrums according to claim 1, wherein said fast axis collimator lens and said slow axis collimator lens collimate the fast and slow axes of the output laser light of the semiconductor laser respectively, said beam rotating element is a microlens array arranged at 45 ° angle for rotating the light beams emitted from the respective light emitting units of the semiconductor laser by 90 ° around the optical axes thereof, and the light transmitting surfaces of said fast axis collimator lens, beam rotating element and slow axis collimator lens are coated with antireflection films, and the transmittance is not less than 99%.
6. The beam combining device according to claim 1, wherein the light transmitting surfaces of the first cylindrical surface transmission lens and the second cylindrical surface transmission lens are coated with an antireflection film, the transmittance is not less than 99%, the first cylindrical surface transmission lens converges the outgoing beam of the semiconductor laser and superimposes the outgoing beam on the transmission grating, and the second cylindrical surface transmission lens converges the reflected beam of the first total reflection mirror and superimposes the reflected beam on the transmission grating.
7. The spectral beam-combining device of claim 1, wherein the light-transmitting surface of the quarter-wave plate is coated with an antireflection film, and the transmittance is greater than or equal to 99%.
8. The spectral beam combining apparatus of claim 1, wherein the transmission grating is disposed at a Littrow angle with respect to an optical axis of an outgoing beam of the semiconductor laser.
9. The spectral beam-combining device of claim 1, wherein the first total reflection mirror and the second total reflection mirror are coated with a highly reflective film having a reflectivity of >99%.

Description

Novel open-loop external cavity spectrum beam combining device of semiconductor laser Technical Field The invention relates to the technical field of semiconductor lasers, in particular to a novel open-loop external cavity spectrum beam combining device of a semiconductor laser. Background The semiconductor laser has the advantages of high electro-optical conversion efficiency, small volume, compact structure, long service life and the like, and is widely applied to the fields of national defense, medical treatment, communication, 3D printing, industrial processing and the like. However, the semiconductor laser chip has a special waveguide structure, so that the light beam quality difference between the fast axis and the slow axis is larger, and the space brightness is lower. The spatial brightness of a semiconductor laser is positively correlated with the beam quality, and how to improve the beam quality of the semiconductor laser is always a research hot spot at home and abroad. The semiconductor laser external cavity spectrum beam combining technology is an effective mode for realizing high beam quality and high brightness output, and multiple paths of lasers with different wavelengths are simultaneously realized in a near field and a far field by utilizing the dispersion effect of a grating to obtain combined laser with beam quality close to that of a single light-emitting unit and output power being the sum of all the light-emitting units. At present, the mode of carrying out the spectrum beam combination of the outer cavity of the semiconductor laser based on diffraction gratings (including reflection diffraction gratings and transmission diffraction gratings, hereinafter referred to as reflection gratings and transmission gratings for short) mainly comprises two structures, namely a closed-loop outer cavity and an open-loop outer cavity. The closed loop external cavity is shown in fig. 1, the polarization direction of the output light beam of the semiconductor laser is consistent with the polarization direction with highest diffraction efficiency of the grating, the partially-reflected output coupling mirror 14 is arranged in the-1 st diffraction direction of the grating, and partial-1 st diffraction light is fed back to the semiconductor laser by the output coupling mirror 14 to realize wavelength locking, and the residual light is output as a combined light beam. However, in this structure, the 0 th and 1 st diffraction orders of the grating do not participate in feedback and the beam combination output is wasted, which affects the beam combination efficiency. The open-loop external cavity is shown in fig. 2, the external cavity does not contain a partially-reflected output mirror, the polarization direction of the output beam of the semiconductor laser is consistent with the polarization direction of the highest diffraction efficiency of the grating, most of the beam is output along the-1-order diffraction direction of the grating in the figure, the 0-order diffraction beam transmitted through the grating is reflected by the first total reflection mirror 9 and returns to the diffraction grating 6 again, a part of the light is returned to the semiconductor laser as part of feedback light through the grating, a part of the light is taken as part of the output beam along the-1-order diffraction direction of the grating in the figure (the direction is the-1-order diffraction direction relative to the incident beam), a part of the light is diffracted along the-1-order diffraction direction of the grating in the figure (the direction is the-1-order diffraction direction relative to the incident beam), after the light is reflected by the second total reflection mirror 10 and returns to the first total reflection mirror 9 again, and the rest of the output beam returns to the first total reflection mirror returns to the round-reflection mirror 6 again, and the semiconductor array returns to the first total reflection mirror 1-order diffraction beam along the 1-order diffraction direction of the grating again as part of the laser light in the direction (the direction is the direction of the incident beam relative to the first total reflection mirror). The structure avoids the waste of 0-order diffraction light and 1-order diffraction light, part of the 0-order diffraction light and 1-order diffraction light is used as feedback light beams for realizing wavelength locking, and meanwhile, part of the 0-order diffraction light and 1-order diffraction light are combined with-1-order diffraction light for output. However, in the structure, the external cavity feedback process is multi-beam superposition feedback, and the feedback beam is formed by a plurality of beams returned to the semiconductor laser, so that the difficulty in locking the wavelength of each light-emitting unit of the semiconductor laser is high, and the conditions that the wavelength locking effect is poor, even part of light-emitting units c