CN112928588A

CN112928588A - Multi-wavelength laser

Info

Publication number: CN112928588A
Application number: CN202110097931.8A
Authority: CN
Inventors: 张笑琪; 张海青; 朱健强; 张艳丽; 张昆鹏; 张国文
Original assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Current assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Priority date: 2021-01-25
Filing date: 2021-01-25
Publication date: 2021-06-08
Anticipated expiration: 2041-01-25
Also published as: CN112928588B

Abstract

A multi-wavelength laser comprising: the imaging structure comprises a resonant cavity, a gain medium and a pumping source; the optical element on the object plane or the image plane of the imaging structure cavity is plated with films with different reflectivities aiming at different wavelengths, so that the loss of each wavelength in each film coating area is different, the condition that only one wavelength starts to vibrate in different film coating areas is met, the laser can output laser with different wavelengths simultaneously, and the space occupation ratio, the shape occupation ratio and the energy occupation ratio of various wavelengths are controlled by laser film coating. The invention realizes multi-wavelength output with freely adjustable space ratio and energy ratio, simultaneously makes the distribution areas of the laser with different wavelengths in the gain medium different, and avoids competition of each wavelength.

Description

Multi-wavelength laser

Technical Field

The invention relates to the field of lasers, in particular to a multi-wavelength laser.

Background

The dual-wavelength laser is applied to the fields of laser medical treatment, laser spectroscopy, laser radar, laser measurement, nonlinear frequency conversion (terahertz) and the like. The main principle of generating dual wavelengths at present is that the gains of different emission peaks (different wavelengths) of a gain medium are different, and the dual wavelengths are obtained by increasing the transmittance of a pump and controlling an output mirror so that the gain of the emission peak with weaker gain exceeds an oscillation threshold, but the dual wavelengths of the dual-wavelength laser are all in a low-order transverse mode and in the same spatial domain, the two wavelengths are in a competition state, and only one wavelength with the largest gain can start oscillation near the pump threshold.

Principle of the invention

In the traditional laser, because the loss difference between the transverse modes of different orders is large, only a few transverse modes of low orders can be generated, so that the multi-wavelength generated in the cavity of the traditional laser is in the same space, and because the multi-wavelength is in the same space, competition can be generated, the output of different wavelengths is unstable, and the energy ratio cannot be controlled; conventional lasers typically produce at most two wavelengths and are produced by the two largest gain peaks of the gain medium. The laser cavity type of the imaging structure cavity has the advantages that the gains and losses of different transverse modes are basically the same, tens of thousands of transverse modes can be supported to start oscillation at the same time, the optical elements on the imaging surface of the imaging cavity are plated with light with different wavelengths, the reflectivity or the transmissivity is different, the loss difference is guaranteed to be large, only laser oscillation with one wavelength is started in the film plating area, and the size, the shape and the energy ratio of the oscillation areas with different wavelengths can be realized through film plating.

Disclosure of Invention

The invention provides a novel multi-wavelength laser which is characterized in that the distribution areas of lasers with different wavelengths in a gain medium are different by utilizing a resonant cavity with an imaging structure and a cavity mirror coating process, so that the competition of each wavelength is avoided; and the space ratio, the shape and the energy ratio of different wavelengths can be adjusted relatively freely. Such an heterospatial multiwavelength laser can produce particular effects in interacting with substances. For example, in the laser medical treatment process, different tissues react differently to laser with different wavelengths, and particularly, the adjacent tissues are important, so that the tissue can be treated at one time, and damage to other components in the multiple action process of single-wavelength laser is avoided. In addition to medical treatment, efficiency can be greatly improved in industrial processing, especially in mass production of special-shaped parts.

The technical solution of the invention is as follows:

a novel multi-wavelength laser comprising: the optical element on the object surface of the imaging structure cavity is plated with films with different reflectivities aiming at different wavelengths, so that the loss of each wavelength in each film coating area is different, the requirement that only one wavelength starts to vibrate in different film coating areas is met, the laser can output laser with different wavelengths simultaneously, and the space occupation ratio, the shape occupation ratio and the energy occupation ratio of various wavelengths can be controlled through laser film coating.

The imaging structure resonant cavity is an imaging system with a lens or other binary optical element. Generally, the object plane, the image plane and the spectrum plane (4F system), but may be composed of the object plane and the spectrum plane (half 4F system).

The resonant cavity of the imaging structure can be realized by a lens, and can also be realized by other optical elements such as a binary optical element and the like.

The pumping source is used for exciting the laser gain medium and can adopt a side pumping mode or an end pumping mode.

The optical element on the object plane of the imaging structure resonant cavity can be designed according to actual requirements, the surface of the optical element is plated with a structural laser film, the reflectivity of lasers with different wavelengths is different, so that the loss of each wavelength is different (the reflection reducing effect can be designed especially for lasers with other wavelengths), and therefore the oscillation starting of only one wavelength in the region is realized, further, the lasers with different wavelengths work in the laser gain medium in regions, the mutual competition is avoided, and the proportion of the lasers with each wavelength in the total output energy can be conveniently adjusted through the cavity mirror film coating.

The coating films of the optical elements in the multi-wavelength laser can be selected according to actual conditions, for example, two end faces of a gain medium with a better special-shaped gain medium are coated with laser films with anti-reflection function on laser, if an end face pumping structure is selected, the laser film with high transmission on pumping light can be also selected to be coated, and if the end face of the gain medium is used as an object plane, the end face of the gain medium is coated with films with different reflectivity on laser with different wavelengths.

The gain medium may be any medium capable of generating laser light, including a single crystal gain medium, a laser ceramic gain medium, a laser glass gain medium, and the like.

The gain medium can also be a composite structure or a composite structure with holes. The composite structure means that laser doped ions in the laser gain medium can be distributed to a certain extent, for example, the middle part of the laser gain medium is not doped with the laser ions, and the periphery is doped; for example, different laser ions can be doped in different regions; also for example, the end caps at both ends of the laser gain medium may be undoped with laser ions, etc.

The multi-wavelength laser can also comprise elements such as an electro-optical switch, a wave plate, a polarizer and the like, and is used for multi-wavelength Q-switched output.

The multi-wavelength laser can also add a structured light hole on the surface of a frequency spectrum to adjust the distribution of a laser transverse mode.

Compared with the prior art, the invention realizes multi-wavelength output with freely adjustable space ratio and energy ratio, simultaneously leads the distribution areas of the laser with different wavelengths in the gain medium to be different, and avoids the competition of each wavelength. Such an heterospatial multiwavelength laser can produce particular effects in interacting with substances.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a simplified schematic diagram of the present invention

FIG. 2 a: example a structure schematic diagram, a multi-wavelength laser of 4F structure

FIG. 2 b: in the first embodiment, the schematic diagram of the coating of the total reflection mirror

FIG. 2 c: in the first embodiment, the coating of the output mirror is schematically shown

FIG. 3: oscillator schematic using binary optical element as frequency domain conversion

FIG. 4: schematic diagram of half 4F structure multi-wavelength laser

FIG. 5: composite gain medium with high middle doping concentration and low edge doping concentration

FIG. 6: composite structure laser gain medium with end caps at two ends, no doping of end caps, and hole in central region

FIG. 7: q-switched structure schematic diagram of multi-wavelength laser

1, an imaging resonant cavity; 2: a gain medium; 3: a pump source; 4: a total reflection mirror; 5: an output mirror; 6: a lens f 1; 7: a lens f 2; 8: a binary optical element 1; 9: a binary optical element 2; 10: a gain medium having a distribution of doping concentrations; 11: a gain medium with an end cap; 12: an electro-optical switch; 1/4 wave plates; 14: PBS polarization beam splitter prism

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. The invention will be further illustrated and described with reference to the drawings and preferred embodiments of the description, without thereby limiting the scope of the invention.

The first embodiment is as follows:

this embodiment is a multi-wavelength and multi-wavelength laser, as shown in fig. 2a, the laser multi-wavelength and multi-wavelength laser includes: the device comprises an imaging resonant cavity (1), a gain medium (2), a pumping source (3), a total reflection mirror (4), an output mirror (5), a lens f1(6) and a lens f2 (7).

The resonant cavity (1) of the imaging structure can accommodate more high-order modes when the cutoff frequency of the imaging system is higher, and the loss of the high-order modes and the loss of the low-order modes are determined by the structure of the imaging cavity. In this embodiment, the two object planes of the resonator of the imaging structure are the holophote and the output mirror. Fig. 2(b) and 2(c) are schematic diagrams of the coating of the reflector and the coating of the output mirror, and the total reflection mirror and the output mirror are different for the coatings with different wavelengths, so that the laser with different wavelengths can start to oscillate in different areas of the gain medium, wherein the wavelength 1 corresponds to the low-order mode of the laser, and the wavelength 2 corresponds to the high-order mode of the laser.

Example two:

fig. three shows an embodiment in which the binary optical element 1(8) and the binary optical element 2(9) are used instead of the normal lens. The binary optical element can replace a traditional lens and has high diffraction efficiency. Other devices that can replace lenses to produce fourier transforms and reduce diffraction losses of spatial high frequency information are also included within the scope of the claims.

Example three:

fig. 4 is a half 4F system configuration, with the object plane being the output mirror and the spectral plane being the total reflection mirror. The gain medium is located between the lens and the output mirror.

Example four:

the embodiment is an example of a multi-wavelength Q-switched laser, and an electro-optical switch, an 1/4 wave plate and a polarization beam splitter prism PBS are added on the basis of the embodiment one for Q-switching. The way of adjusting the Q may also be changed, for example, at the PBS, the cavity design is reversed, and the output mirror may be replaced by a total reflection mirror; for example, the method can be realized by directly using an electro-optical switch without using a wave plate; other ways of adjusting Q are also within the scope of the patent claims.

Fig. 5 is a schematic diagram of a composite gain medium with a low doping concentration in the middle region and a high doping concentration in the edge region. Fig. 6 is a composite structure laser gain medium with end caps at both ends, the end caps being undoped and the central region being open.

Claims

1. A multi-wavelength laser comprising: the device comprises an imaging structure resonant cavity (1), a gain medium (2) and a pumping source (3); the optical element on the object plane or the image plane of the imaging structure cavity (1) is coated with films with different reflectivities aiming at different wavelengths, so that the loss of each wavelength in each coating area is different, the condition that only one wavelength starts to vibrate in different coating areas is met, the laser can output laser with different wavelengths simultaneously, and the space occupation ratio, the shape occupation ratio and the energy occupation ratio of various wavelengths are controlled by laser coating.

2. The multiwavelength laser of claim 1, wherein the imaging structure cavity (1) is an imaging system with a lens or other binary optical element.

3. The multiwavelength laser of claim 2, wherein the imaging structure cavity (1) consists of object, image and spectral planes (4F system), or object and spectral planes (half 4F system).

4. The multiwavelength laser of claim 1, wherein the resonant cavity (1) of the imaging structure comprises a lens or a binary optical element.

5. The multiwavelength laser of claim 1, wherein the pump source (3) is configured to pump the laser gain medium in a side-pumped or end-pumped manner.

6. The multiwavelength laser of claim 1, wherein said gain medium (2) is any lasing medium, including single crystal gain media, laser ceramic gain media, laser glass gain media, and the like.

7. The multiwavelength laser of claim 1, wherein the gain medium (2) is a composite structure or a holey composite structure. The composite structure means that laser doped ions in the laser gain medium can be distributed to a certain extent, for example, the middle part of the laser gain medium is not doped with the laser ions, and the periphery is doped; for example, different laser ions can be doped in different regions; also for example, the end caps at both ends of the laser gain medium may be undoped with laser ions, etc.

8. The multiwavelength laser of claim 1, further comprising a structured aperture at the spectral plane for adjusting the transverse mode profile of the laser.

9. The multiwavelength laser of claim 1, further comprising an electro-optic switch, a waveplate, a polarizer for the multiwavelength Q-switched output.