CN104393486A - Adjustment device and method for optical path of external cavity semiconductor laser - Google Patents

Abstract

An external cavity semiconductor laser optical path adjustment device and adjustment method relate to an external cavity semiconductor laser. The adjustment device is provided with a semiconductor gain device, a collimator lens, a beam splitter, a light splitting element, a focusing lens, a CCD camera and a display screen. Adjustment method: move the beam splitter into the optical path; collimate the laser beam emitted by the semiconductor gain device and shoot it to the beam splitter; the transmitted light undergoes multi-level diffraction on the beam splitter, and the first-order diffraction is adjusted by adjusting the angle of the beam splitter The light is fed back to the vicinity of the cavity surface of the semiconductor gain device; the reflected light passing through the beam splitter is focused on the CCD camera by adjusting the focusing lens, and the size and Finally, the feedback spot and the surface of the inner cavity completely coincide to obtain the best state of the optical path of the external cavity laser; after the adjustment of the optical path is completed, the beam splitter is moved out of the optical path again to avoid the loss of output light of the external cavity laser.

Description

An external cavity semiconductor laser optical path adjustment device and adjustment method

technical field

The invention relates to an external cavity semiconductor laser, in particular to an external cavity semiconductor laser for observing and analyzing the external cavity feedback light spot and the internal cavity surface of a semiconductor gain device by adding a micro-region image analysis optical path to the optical path of the external cavity semiconductor laser Optical path adjustment device and adjustment method.

Background technique

External cavity semiconductor lasers are a type of laser light source made with external optical components as optical feedback and mode selection components. This type of laser light source has the advantages of high spectral purity, tunable lasing wavelength, high efficiency, and good reliability. Communication, optical measurement, optical storage and other fields have broad application prospects. Among them, accurately feeding the external feedback light back to the active region of the semiconductor gain device to make it interact with the active medium has an important impact on the output power and stability of the external cavity semiconductor laser.

The optical path adjustment of the traditional external cavity semiconductor laser relies on direct observation of the collimated state of the beam and the position of the feedback light with the naked eye. coincidence, resulting in a sudden increase in the intensity of the output beam, and finally achieve external cavity lasing. In the process of debugging the optical path of the external cavity with the traditional method, the size and specific position of the light spot on the cavity surface of the feedback semiconductor gain device cannot be judged. optimal coupling. Therefore, it is extremely important to develop a convenient and practical external cavity optical path debugging method for improving the performance of external cavity semiconductor lasers.

Guo Shuguang (Guo Shuguang. Research on Compact Photon Sources. Doctoral Dissertation of Nankai University, April 2001, 26-28) introduced some work and content on improving the performance of lasers, including: weak Littrow and Littman structures in the 80Onm band Experimental research on coupled tunable external cavity semiconductor lasers; systematically analyzed the influence of the positioning error of the non-mode-hopping tuning structure of external cavity semiconductor lasers on the range of non-mode-hopping tuning and designed a set of large-scale non-mode-hopping tuning external cavity semiconductor laser experiments system; analyzed three types of sinusoidal mechanisms in grating spectroscopy instruments and designed Littrow and Littman external cavity semiconductor laser tuning mechanisms that can achieve linear wavelength scaling; using fiber Bragg gratings as external cavity feedback elements for tunable fiber Bragg grating external cavity Performance studies of semiconductor lasers; application of Littrow grating tuning techniques to the characteristics of Yb ³⁺ -doped double-clad fiber lasers; two types of optical ballasts are described. It also gives the experimental research of weakly coupled grating external cavity semiconductor lasers in the 800nm band, and discusses the debugging methods of external cavity semiconductor lasers.

Contents of the invention

The object of the present invention is to provide an external cavity semiconductor laser optical path adjustment device and adjustment method.

The optical path adjustment device of the external cavity semiconductor laser is provided with a semiconductor gain device, a collimating lens, a beam splitter, a light splitting element, a focusing lens, a CCD camera and a display screen;

The semiconductor gain device, collimator lens, beam splitter, and beam splitter are arranged coaxially in sequence, the focusing lens and the CCD camera are sequentially arranged on the reflected light path of the beam splitter, and the output port of the CCD camera is connected to the input end of the display screen.

The semiconductor gain device is a semiconductor light-emitting device with optical gain, including but not limited to edge-emitting semiconductor lasers, superluminescent light-emitting diodes, optical amplifiers, and the like.

The collimator lens is an optical lens with optical collimation function, which can collimate the light beam emitted by the semiconductor gain device into a parallel light beam, including but not limited to aspheric lens, doublet lens, objective lens and so on.

The beam splitter is less than 1 mm in thickness, and can divide the incident light beam into an optical element with two beams of light, transmission and reflection, and the light intensity ratio of the two beams of transmission and reflection is preferably 1:1; the beam splitter is installed On an object table, it can be moved in and out of the optical path system, that is, when adjusting the external cavity optical path, move it into the optical path system, and move it out of the optical path system after adjustment, so as to avoid light loss when the external cavity laser is used. Due to the small thickness of the beam splitter, the influence of moving the beam splitter in and out of the external cavity optical system can be ignored.

The light splitting element can be a diffraction grating.

The focusing lens is an optical lens with an optical focusing function, which can focus the light beam in the CCD camera, including but not limited to a convex lens or a plano-convex lens with a focal length of 5 cm.

The CCD camera is located at the focal point of the focusing lens, so that the feedback light spot of the external cavity and the cavity surface of the semiconductor gainer are imaged on the surface of the CCD camera.

The display screen is connected with a CCD camera, and the external cavity feedback spot imaged in the CCD camera and the image of the inner cavity surface of the semiconductor gain device can be observed on the display screen.

The external cavity semiconductor laser optical path adjustment device can intuitively reflect the light spot and the inner cavity surface of the semiconductor gain device fed back by the light splitting element on the display screen. Under the guidance of the image on the display screen, the collimator lens and The multi-dimensional state micro-adjustment of the light splitting element can easily adjust the size and position of the feedback spot, and finally make the feedback spot coincide with the inner cavity surface of the semiconductor gain device, and obtain the best external cavity laser optical path, thereby improving the performance of the external cavity semiconductor laser .

The method for adjusting the optical path of the external cavity semiconductor laser comprises the following steps:

Step 1: When adjusting the optical path of the external cavity semiconductor laser, move the beam splitter into the optical path by translating or rotating the stage;

Step 2: The laser light emitted by the semiconductor gain device is collimated through the collimator lens and then directed to the beam splitter. At this time, part of the laser light intensity passes through the beam splitter mirror to the beam splitter element, and the other part of the laser light intensity is passed through the beam splitter mirror. After reflection, it goes to the focusing lens;

Step 3: The transmitted light undergoes multi-level diffraction on the light-splitting element, and the first-order diffracted light is fed back to the vicinity of the cavity surface of the semiconductor gain device by adjusting the angle of the light-splitting element;

Step 4: Focus the reflected light passing through the beam splitter into the CCD camera by adjusting the focusing lens. At this time, the inner cavity surface of the semiconductor gain device and the outer cavity feedback spot of the light splitting element can be displayed on the display screen. The collimator lens and the light splitting element are fine-tuned in multi-dimensional state, and the size and position of the feedback spot are adjusted, so that the feedback spot and the inner cavity surface are completely coincident, and the best state of the optical path of the external cavity laser is obtained;

Step 5: After the optical path adjustment of the external cavity semiconductor laser is completed, the beam splitter is moved out of the optical path by translating or rotating the stage again to avoid loss of the output light of the external cavity laser.

The invention can be applied to the optical path used by Littrow, Littman grating external cavity semiconductor lasers and external cavity semiconductor lasers composed of other components, and is used for assisting the adjustment of the optical path.

The invention uses a CCD camera to image the feedback spot of the external cavity and the cavity surface of the semiconductor gain device, so that the size and position of the feedback spot on the cavity surface of the semiconductor gain device can be observed on the display screen. The multi-dimensional state micro-adjustment of the optical components makes the external feedback spot accurately feedback back to the active area, so that it can effectively interact with the active medium, which is conducive to improving the power and stability of the external cavity semiconductor laser.

The invention can intuitively reflect the external cavity feedback light spot and the internal cavity surface of the semiconductor gain device on the display screen, facilitates the adjustment of the coincidence of the two, is helpful for the optical path adjustment of the external cavity semiconductor laser, and further improves the adjustment accuracy of the external cavity optical feedback, Improving the performance of external cavity semiconductor lasers. The invention is simple, intuitive and effective, and has strong practical value.

Description of drawings

FIG. 1 is a schematic structural diagram of Embodiment 1 of an optical path adjustment device for an external cavity semiconductor laser of the present invention.

Fig. 2 is a schematic diagram of the application of the present invention in the optical path of a Littrow-type grating external cavity semiconductor laser (embodiment 2).

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1

Referring to FIG. 1 , an embodiment of an external cavity semiconductor laser optical path adjustment device includes a semiconductor gain device 1 , a collimating lens 2 , a beam splitter 3 , a beam splitting element 4 , a focusing lens 5 , a CCD camera 6 and a display screen 7 .

The semiconductor gain device 1, collimating lens 2, beam splitter 3, and light splitting element 4 are arranged coaxially in sequence, the focusing lens 5 and the CCD camera 6 are arranged on the reflected light path of the beam splitter 3 in turn, and the output port of the CCD camera 6 Connect to the input terminal of display screen 7.

The semiconductor gain device 1 is a semiconductor light-emitting device with optical gain, including but not limited to edge-emitting semiconductor lasers, superluminescent light-emitting diodes, optical amplifiers, and the like.

The collimator lens 2 is an optical lens with optical collimation function, which can collimate the beam emitted by the semiconductor gain device 1 into a parallel beam, including but not limited to an aspheric lens, a doublet lens, an objective lens, and the like.

The beam splitter 3 is an optical element with a thickness less than 1 mm and can split the incident light beam into two beams of transmitted and reflected light. The light intensity ratio of the two beams of transmitted and reflected light is preferably 1:1.

The beam splitter 3 is installed on an object stage and can be moved in and out of the optical path system, that is, when the external cavity optical path is adjusted, it is moved into the optical path system, and after the adjustment is completed, it is moved out of the optical path system to avoid the use of the external cavity laser. light loss. Since the thickness of the beam splitter 3 is small, the influence of moving in and out of the beam splitter 3 on the optical system of the external cavity can be ignored.

The light splitting element 4 adopts a diffraction grating.

The focusing lens 5 is an optical lens with optical focusing function, which can focus the light beam in the CCD camera 6, including but not limited to a convex lens or a plano-convex lens with a focal length of 5 cm.

The CCD camera 6 is located at the focal point of the focusing lens 5 , so that the external cavity feedback light spot and the inner cavity surface of the semiconductor gain device 1 are imaged on the surface of the CCD camera 6 .

The display screen 7 is connected with the CCD camera 6 , and the external cavity feedback spot imaged in the CCD camera 6 and the image of the inner cavity surface of the semiconductor gain device 1 can be observed on the display screen 7 .

The external cavity semiconductor laser optical path adjustment device can intuitively reflect the light spot and the inner cavity surface of the semiconductor gain device 1 fed back by the light splitting element 4 on the display screen 7, and under the guidance of the image on the display screen 7, it can be adjusted The collimator lens 2 and the light splitting element 4 are micro-adjusted in multi-dimensional state, so as to conveniently adjust the size and position of the feedback spot, and finally make the feedback spot coincide with the inner cavity surface of the semiconductor gain device, and obtain the best external cavity laser optical path, thereby improving Performance of external cavity semiconductor lasers.

The method for adjusting the optical path of an external cavity semiconductor laser in this embodiment includes the following steps:

Step 1: When adjusting the optical path of the external cavity semiconductor laser, move the beam splitter 3 into the optical path by translating or rotating the stage;

Step 2: The laser light emitted by the semiconductor gain device 1 is collimated by the collimator lens 2 and then directed to the beam splitter 3. At this time, a part of the laser light intensity passes through the beam splitter 3 to the beam splitting element 4, and the other part of the laser light After being strongly reflected by the beam splitter 3, it goes to the focusing lens 5;

Step 3: The transmitted light undergoes multi-level diffraction on the light splitting element 4, and the first-order diffracted light is fed back to the vicinity of the cavity surface of the semiconductor gain device 1 by adjusting the angle of the light splitting element 4;

Step 4: Focus the reflected light passing through the beam splitter 3 into the CCD camera 6 by adjusting the focusing lens 5, and the inner cavity surface of the semiconductor gain device 1 and the outer surface of the light splitting element 4 can be displayed on the display screen 7 at this time. The cavity feedback spot, by fine-tuning the multi-dimensional state of the collimating lens 2 and the beam splitting element 4, adjusts the size and position of the feedback spot, and finally makes the feedback spot completely coincide with the inner cavity surface, and obtains the best state of the optical path of the external cavity laser;

Step 5: After the optical path adjustment of the external cavity laser is completed, the beam splitter 3 is moved out of the optical path by translating or rotating the stage again to avoid loss of the output light of the external cavity laser.

In practice, the adjustment device can intuitively reflect the light spot of the semiconductor gain device 1 after being fed back by the light splitting element 4 and the inner cavity surface of the semiconductor gain device 1 on the display screen 7, which is convenient for adjusting the overlap of the two, and helps the external cavity The optical path adjustment of the semiconductor laser can further improve the adjustment accuracy of the external cavity optical feedback and improve the performance of the external cavity semiconductor laser.

An external cavity semiconductor laser optical path adjustment device and adjustment method provided by the present invention can be applied to the optical path used by Littrow, Littman grating external cavity semiconductor lasers and external cavity semiconductor lasers composed of other components to improve Performance of external cavity semiconductor lasers.

Example 2

As shown in Figure 2, similar to Embodiment 1, the difference is that the light splitting element adopts a diffraction grating 41, and the present invention is applied to the optical path of a Littrow-type grating external cavity semiconductor laser, mainly including: a semiconductor gain device 11, a collimator Lens 21 , beam splitter 31 , diffraction grating 41 , focusing lens 51 , CCD camera 61 and display screen 71 .

The semiconductor gain device 11 is a semiconductor light emitting device with optical gain, and an edge-emitting semiconductor laser diode coated with an anti-reflection film on the surface of the optical cavity can be selected.

The collimator lens 21 is an optical lens with optical collimation function, which can collimate the beam emitted by the semiconductor gain device 11 into a parallel beam, and an aspheric lens with a numerical aperture of 0.5 can be selected.

The beam splitter 31 is an optical element with a thickness less than 1mm, which can split the incident light beam into two beams of light with a certain intensity ratio of transmission and reflection, and the ratio of transmission and reflection light intensity can be selected to be 1:1.

The beam splitter 31 is installed on a rotating stage, and can be moved in and out of the optical path system, that is, when the optical path of the external cavity is adjusted, the beam splitter 31 is moved into the optical path of the external cavity, and then moved out of the optical path system after adjustment to avoid external Light loss when cavity lasers are used. Since the thickness of the beam splitter 31 is small, the influence of moving in and out of the beam splitter 31 on the optical system of the external cavity can be ignored.

The diffraction grating 41 is an optical element with a dispersion and light splitting effect, and its first-order diffracted light can be fed back to the semiconductor gain device along the direction of the incident light.

The focusing lens 51 is an optical lens with an optical focusing function, which can focus the light beam in the CCD camera 61, and a convex lens with a focal length of 5 cm can be selected.

The CCD camera 61 is located at the focal point of the focusing lens 51 , so that the external cavity feedback light spot and the internal cavity surface of the semiconductor gain device 11 are imaged on the surface of the CCD camera 61 .

The display screen 71 is connected with the CCD camera 61 , and the external cavity feedback spot imaged in the CCD camera 61 and the image of the cavity surface of the semiconductor gain device 11 can be observed on the display screen 71 .

A method for adjusting the optical path of an external cavity semiconductor laser provided in this embodiment includes the following steps:

Step 1: When adjusting the optical path of the Littrow grating external cavity semiconductor laser, move the beam splitter 31 into the optical path by rotating the stage.

Step 2: Increase the operating current of the semiconductor gain device 11 to its lasing, and the emitted laser light is collimated by the collimator lens 21 and then directed to the beam splitter 31. At this time, a part of the laser light intensity passes through the beam splitter 31 and is directed towards the diffraction The grating 41, the other part of the laser light intensity is reflected by the beam splitter 31 and then directed to the focusing lens 51; here, the beam splitter 31 with a thickness of less than 1 mm is selected to avoid changes in the optical path of the external cavity after the beam splitter 31 is removed.

Step 3: The transmitted light undergoes multi-level diffraction on the diffraction grating 41 , and the first-order diffracted light is fed back to the vicinity of the cavity surface of the semiconductor gain device 11 by adjusting the angle of the diffraction grating 41 .

Step 4: Focus the reflected light passing through the beam splitter 31 on the CCD camera 61 by adjusting the focusing lens 51. At this time, the inner cavity surface of the semiconductor gain device 11 and the outer surface of the diffraction grating 41 can be displayed on the display screen 71. For the cavity feedback spot, by fine-tuning the multi-dimensional state of the collimator lens 21 and the diffraction grating 41, the diffraction spot can completely coincide with the surface of the inner cavity, and the best state of the optical path of the outer cavity can be obtained.

Step 5: After the optical path adjustment of the Littrow-type grating external cavity semiconductor laser is completed, the beam splitter 31 is moved out of the optical path by rotating the stage to avoid loss of the output light of the external cavity laser.

Claims (9)

1. an external-cavity semiconductor laser optical path adjustment device, is characterized in that being provided with semiconductor gain device, collimating lens, beam splitter, beam splitter, condenser lens, ccd video camera and display screen;

Described semiconductor gain device, collimating lens, beam splitter, beam splitter arranged in co-axial alignment successively, condenser lens and ccd video camera are located on the reflected light path of beam splitter successively, and the output port of ccd video camera connects the input of display screen.

2. a kind of external-cavity semiconductor laser optical path adjustment device as claimed in claim 1, it is characterized in that described semiconductor gain device is the light emitting semiconductor device with the gain of light, include but not limited to edge-emission semiconductor laser, super-radiance light emitting diode, image intensifer.

3. a kind of external-cavity semiconductor laser optical path adjustment device as claimed in claim 1, it is characterized in that described collimating lens is the optical mirror slip with optical alignment effect, the beam collimation that semiconductor gain device can be sent is collimated light beam, includes but not limited to non-spherical lens, cemented doublet, objective lens.

4. a kind of external-cavity semiconductor laser optical path adjustment device as claimed in claim 1, is characterized in that described beam splitter is that thickness is less than 1mm, incident beam can be divided into the optical element with transmission and reflection two-beam; Described beam splitter is installed on an articles holding table, can shift out by shift-in in light path system, is moved into light path system when namely adjusting external cavity optical path.

5. a kind of external-cavity semiconductor laser optical path adjustment device as claimed in claim 4, is characterized in that the beam intensity ratio of described transmission and reflection two-beam is 1: 1.

6. a kind of external-cavity semiconductor laser optical path adjustment device as claimed in claim 1, is characterized in that described beam splitter adopts diffraction grating.

7. a kind of external-cavity semiconductor laser optical path adjustment device as claimed in claim 1, it is characterized in that described condenser lens is the optical mirror slip with optical focus effect, can focus the light beam in ccd video camera, include but not limited to that focal length is convex lens or the planoconvex spotlight of 5cm.

8. a kind of external-cavity semiconductor laser optical path adjustment device as claimed in claim 1, is characterized in that described ccd video camera is positioned in the focus of condenser lens, makes the inner chamber chamber surface imaging of external cavity feedback hot spot and semiconductor gain device in ccd video camera surface.

9. an external-cavity semiconductor laser optical path adjusting method, it is characterized in that adopting as a kind of external-cavity semiconductor laser optical path adjustment device as described in arbitrary in claim 1 ~ 7, described method of adjustment comprises the following steps:

Step 1: when carrying out light path adjustment to external-cavity semiconductor laser, moves in light path by translation or rotation articles holding table by beam splitter;

Step 2: semiconductor gain device is swashed the laser after penetrating and undertaken collimating rear directive beam splitter by collimating lens, now a part of laser intensity is through beam splitter directive beam splitter, another part laser intensity is by directive condenser lens after beam splitter reflection;

Step 3: transmitted light, on beam splitter, multiorder diffractive occurs, feeds back near face, semiconductor gain inner cavity chamber by regulating the angle of beam splitter by first-order diffraction light;

Step 4: the reverberation through beam splitter is focused in ccd video camera by regulating condenser lens, now demonstrate the face, inner chamber chamber of semiconductor gain device and the external cavity feedback hot spot through beam splitter on a display screen, multi-dimensional state inching is carried out by collimation lens and beam splitter, regulate size and the position of feedback hot spot, finally make feedback hot spot and face, inner chamber chamber overlap completely, obtain the optimum state of outside cavity gas laser light path;

Step 5: after having adjusted external-cavity semiconductor laser light path, by translation again or rotate articles holding table beam splitter is shifted out light path, avoids the output light loss of outside cavity gas laser.