CN114336249A - A Raman laser with precise wavelength tuning by temperature control - Google Patents

Abstract

The present invention provides a Raman laser that realizes fine tuning of output wavelength by adjusting gas temperature. The Raman laser includes: a pump laser for outputting a parallel pump laser beam; a wavelength converter for converting the The pump laser is converted into a Raman laser output, and the wavelength converter is filled with a Raman active gas; a focusing lens is used to focus the pump laser into the wavelength converter; a temperature control module is used to control the The temperature of the wavelength converter; a gas pressure adjusting device for controlling the density of the Raman active gas inside the wavelength converter. The Raman laser provided by the invention can precisely tune the output wavelength of the Raman laser through temperature.

Description

A Raman laser with precise wavelength tuning by temperature control

technical field

The invention belongs to the field of lasers, and in particular relates to a Raman laser capable of realizing precise wavelength tuning through temperature control.

technical background

Laser is a special light source with monochromaticity (single output wavelength), but at present a single type of laser cannot generate all wavelengths. In order to enrich wavelength types and meet different wavelength requirements, it is necessary to The wavelength is converted, and the desired wavelength is generated through the conversion of the wavelength.

Stimulated Raman is an important laser frequency conversion method, and a lot of research and applications have been done on the stimulated Raman laser frequency conversion technology at home and abroad. The large-scale adjustment of Raman frequency conversion achieved is usually more than a few hundred wavenumbers. For example, the vibration Raman frequency shift of gas can reach several thousand wavenumbers, and the rotational Raman frequency shift can be at least hundreds of wavenumbers. Shifts are also usually several hundred wavenumbers. The current research mainly focuses on the large-span adjustment of the wavelength, while in some applications, the wavelength of the output laser needs to be finely and finely adjusted.

SUMMARY OF THE INVENTION

The invention is a laser frequency conversion device, which can realize the fine adjustment of the wavelength of the Raman laser through the temperature change of the gas medium.

The technical scheme of the present invention is as follows:

A Raman laser that realizes fine tuning of the output wavelength through gas temperature adjustment is mainly composed of two parts: a pump laser source and a wavelength converter.

Specifically, the Raman laser includes:

Pump laser, used for pump laser with parallel output beam;

a wavelength converter for converting the pump laser into a Raman laser output, and the wavelength converter is filled with a Raman active gas;

a focusing lens for focusing the pump laser into the wavelength converter;

a temperature control module for controlling the temperature of the wavelength converter;

A gas pressure adjusting device for controlling the density of the Raman active gas inside the wavelength converter.

Among them, the focal length of the focusing lens should match the length of the Raman cell, for example, a one-meter-long Raman cell should use a half-meter-long focusing lens;

Based on the above solution, preferably, the temperature control module includes a temperature controller and a temperature controller power supply; the temperature controller is in large-area contact with the tube wall of the wavelength converter by winding, socketing or bolting; The temperature controller power supply supplies power for the temperature controller;

The air pressure regulating device includes a gas pressure gauge and a gas pressure charging and discharging valve; the gas pressure gauge is used to read the gas pressure in the wavelength converter; the gas pressure charging and discharging valve is used to control the gas inside the wavelength converter of charging and discharging.

Based on the above solution, preferably, the temperature control method of the temperature control module is electrical temperature control or fluid liquid temperature control.

Based on the above solution, preferably, the electrical temperature control method is electric heating or semiconductor refrigeration; the flow liquid temperature control method is heating or cooling through a liquid flowing medium.

The temperature controller and the temperature controller power supply can not only control the temperature rise of the wavelength converter but also lower the temperature of the wavelength converter, and the temperature control is a temperature-adjustable device.

Based on the above solution, preferably, as shown in FIG. 1 of the accompanying drawings: the wavelength converter includes a Raman cell, and the central axis of the Raman cell along the length direction coincides with the central axis of the pump laser beam ; Two ends of the Raman cell along the beam transmission direction are respectively installed with a Raman cell window 1 and a Raman pool window 2. The central axis of the Raman cell window 1 and the Raman cell window 2 should be ensured to coincide with the central axis of the pump laser beam; two connecting pipes are welded on both sides of the Raman cell, which are respectively connected to the barometer and the gas charging and discharging valve.

Based on the above solution, preferably, the Raman cell is a hollow tubular container; the Raman cell can withstand high pressure, and the pressure range is 0.01-5.00 MPa.

The surface of the first Raman cell window is coated with a pump laser antireflection film; the surface of the second Raman cell window is coated with a pump laser and a Raman laser antireflection film.

Based on the above scheme, preferably, as shown in Figure 2 of the accompanying drawings: the Raman cell is divided into two parts, denoted as the input end of the Raman pool and the output end of the Raman pool; the input end of the Raman pool and the Raman pool output end; A photonic crystal fiber is arranged between the output ends of the Mann cell; both ends of the photonic crystal fiber are connected with a fixed tube; the two fixed tubes are respectively connected with the input end of the Raman cell and the output end of the Raman cell and are fixed ; The central axis of the two fixed tubes along the length direction coincides with the central axis of the pumping laser beam;

The focusing lens collects the pump laser into the photonic crystal fiber, and generates a Raman laser output after passing through the photonic crystal fiber;

The gas pressure adjusting device controls the density of the Raman active gas inside the photonic crystal fiber through the input end of the Raman cell and the output end of the Raman cell; the temperature control module is used for controlling the temperature of the photonic crystal fiber.

Among them, the photonic crystal fiber is designed to meet the low-loss transmission of the pump laser wavelength and the Raman laser wavelength through the band gap design.

Based on the above solution, preferably, the Raman active gas includes any one of nitrogen, oxygen, and methane; the output wavelength range of the pump laser is relatively wide, covering any one of ultraviolet light, visible light, and infrared light .

Based on the above solution, preferably, the air pressure adjustment device includes a gas cylinder; the gas cylinder is used to supply the Raman active gas into the wavelength converter.

The above-mentioned Raman laser implementation process is: as shown in Figure 1, after outputting from one end, the pump laser is focused into the Raman cell after passing through the focusing lens, and the Raman laser output is directly generated; or as shown in Figure 2, the pump laser After passing through the focusing lens, the laser light is collected in the hollow-core photonic crystal fiber at one end of the Raman cell, and is output from the other end of the Raman cell to the outside of the Raman cell after passing through the hollow-core photonic crystal fiber.

The gas temperature of the present invention is changed by the temperature control module, and the specific realization process is: the control of the gas temperature is realized by the temperature controller and the power supply of the temperature controller; the devices in FIG. 1 and FIG. 2 are also applicable to the above-mentioned adjustment of the gas temperature method.

The present invention is an invention for realizing laser wavelength conversion through stimulated Raman scattering effect, and various wavelengths of lasers are generated by existing finished lasers (such as: solid Nd:YAG and its frequency doubling, frequency combining, parametric oscillation, etc.). ) as a pump light source, a laser source different from the pump laser is generated after passing through the Raman medium. The key technology is to achieve precise tuning of the Raman conversion wavelength by changing the temperature of the Raman medium. The physical principle is that the energy level population of molecules will change with the change of temperature. For example, the density of methane gas is 0.15001. Under the condition of g/cm ³ , the Raman frequency shift corresponding to the temperature change from 150℃ to 250℃ can be changed from 2914.88cm ^-1 to 2915.23cm ^-1 , so the output wavelength of the Raman laser can be precisely tuned by temperature.

beneficial effect

1. The advantages of the present invention are that (1) the wavelength conversion of the laser can be realized; (2) the wavelength of the Raman laser can be finely adjusted on the basis of the large-scale conversion of the laser wavelength; (3) the photonic crystal fiber is used in the design and other methods can improve the light conversion efficiency of the frequency conversion laser; (4) the cost is low and the structure is simple.

2. The present invention first proposes a method of frequency shift micro-adjustment in Raman laser frequency conversion. The Raman laser wavelength can be finely adjusted by changing the temperature of the Raman medium. Usually, the adjustment accuracy can reach 10 ^-2 cm ^-1 . The invention can realize the large-scale adjustment of the laser wavelength, realize the micro-adjustment of the Raman frequency shift through the temperature control of the medium, and finally realize the precise adjustment of the Raman laser wavelength.

3. The Raman frequency conversion laser of the present invention can be used in the fields of laser frequency conversion and laser wavelength precision tuning. The design is to pass the output wavelength of the existing finished laser through the Raman cell to achieve a large range of wavelengths over thousands of wavenumbers. At the same time, the laser wavelength can be finely tuned within a small range of several wavenumbers by controlling the temperature. This technology can be used in the field of laser frequency conversion, and can be used in some applications that are sensitive to small wavelength shifts, such as the spectral detection of some substances, such as laser transmission in the atmosphere. Water absorption peaks, etc.

Description of drawings

Figure 1. Schematic diagram of the structure of a Raman laser with fine tuning of the output wavelength through gas temperature adjustment (scheme 1);

Figure 2 is a schematic structural diagram of adding a hollow-core photonic crystal fiber inside the Raman cell 5 (plan 2);

The device names in the figure are as follows:

1. Pump laser; 2. Focusing lens; 3. Raman cell window 1; 4. Raman cell window 2; 5. Raman cell; 6. Gas pressure gauge; 7. Air pressure charging and discharging valve; 8. Temperature control 9. Temperature controller power supply; 10. Hollow-core photonic crystal fiber; 11. Fixed tube one; 12. Fixed tube two; 13. Air pressure charging and discharging valve.

Detailed ways

In order to describe the specific working process and using method of the present invention in detail, the specific embodiments of the present invention are illustrated in combination with the actual application situation.

Example 1

As shown in Figure 1, a Raman laser with fine tuning of the output wavelength by gas temperature regulation produces a first-order Stokes laser. A solid Nd:YAG laser with an output wavelength of 1064 nm is used to pump methane to generate a Raman laser that can be finely tuned around 1543 nm.

According to Figure 1 in the accompanying drawings, the working process of the Raman laser is as follows:

The first step: the pump laser is focused and input into the Raman cell;

Step 2: The temperature of methane gas in the Raman cell can be adjusted through the temperature control module;

Step 3: Use a wavelength meter to detect the output Raman laser, and set a reasonable methane gas temperature according to the wavelength.

For example: the corresponding relationship between temperature and Raman frequency shift when the density of methane is 0.15g/ ^cm3 is shown in the following table

Example 2

The IPG commercialized fiber laser is used as the pump laser source with a wavelength of 1070 nm. Through the design scheme in Figure 2, the IPG fiber laser can be focused and collected into a hollow-core photonic crystal fiber, and high-purity methane is charged into the Raman cell. , the 1070nm wavelength laser can be converted to 2840nm, and then the Raman wavelength can be finely tuned around 2840nm by adjusting the temperature of the methane gas. For example, when the temperature range is -100 to 300 °C, the wavelength of the Raman laser can be tuned around 2831 to 2849 nm.

Example 3

According to the design scheme in Figure 2, the hollow-core photonic crystal fiber is added to the Raman cell to reduce the threshold of stimulated Raman and realize the high-efficiency conversion of pump laser.

The implementation process of this scheme can be as follows: use the 532nm laser as the pump laser, fill the Raman cell with high-purity nitrogen gas, collect the 532nm pump laser into the hollow-core photonic crystal fiber through the focusing lens, and pass the gas The temperature control can realize the fine tuning of the Raman laser wavelength around 607nm. For example, when the temperature range is -100～100℃, the Raman laser wavelength can be tuned around 602～610nm.

Claims (9)

1. A raman laser, characterized in that the raman laser comprises:

the pump laser is used for outputting pump laser with parallel light beams;

the wavelength converter is used for converting the pump laser into Raman laser to be output, and Raman active gas is filled in the wavelength converter;

a focusing lens for focusing the pump laser light into a wavelength converter;

the temperature control module is used for controlling the temperature of the wavelength converter;

and the gas pressure regulating device is used for controlling the density of the Raman active gas in the wavelength converter.

2. Raman laser according to claim 1,

the temperature control module comprises a temperature controller and a temperature controller power supply; the temperature controller is in contact with the pipe wall of the wavelength converter in a winding, sleeving or bolt fixing mode; the temperature controller power supply supplies power to the temperature controller;

the air pressure adjusting device comprises an air pressure gauge and an air pressure charging and discharging valve; the gas pressure gauge is used for reading the gas pressure in the wavelength converter; the air pressure charging and discharging valve is used for controlling charging and discharging of air in the wavelength converter.

3. The raman laser according to claim 2, wherein the temperature control means of the temperature control module is an electrically controlled temperature or a temperature controlled by a flowing liquid.

4. A raman laser according to claim 3, wherein said electrical temperature control means is electrical heating or semiconductor cooling; the temperature of the flowing liquid is controlled by heating or cooling through a liquid flowing medium.

5. A raman laser according to claim 1, wherein said wavelength converter comprises a raman cell having a central axis along a length direction coincident with a central axis of said pump laser beam; and a first Raman pool window and a second Raman pool window are respectively arranged at two ends of the Raman pool along the transmission direction of the light beam.

6. A Raman laser according to claim 5, wherein: the Raman pool is a hollow tubular container; the Raman cell can bear high pressure, and the pressure range is 0.01-5 MPa;

a pumping laser antireflection film is plated on the surface of the first Raman cell window; and the surface of the Raman cell window II is plated with a pumping laser and a Raman laser antireflection film.

7. A Raman laser according to claim 5, wherein: the Raman pool is divided into two parts, namely a Raman pool input end and a Raman pool output end; a photonic crystal fiber is arranged between the input end of the Raman cell and the output end of the Raman cell; two ends of the photonic crystal fiber are respectively connected with a fixed tube; the two fixing pipes are respectively communicated and fixed with the input end of the Raman pool and the output end of the Raman pool; the central axes of the two fixed pipes along the length direction are coincident with the central axis of the pump laser beam;

the focusing lens collects the pump laser into the photonic crystal fiber, and Raman laser output is generated after the pump laser passes through the photonic crystal fiber;

the air pressure adjusting device controls the density of Raman active gas in the photonic crystal fiber through the input end of the Raman cell and the output end of the Raman cell; the temperature control module is used for controlling the temperature of the photonic crystal fiber.

8. A raman laser according to claim 1, wherein said raman active gas comprises any one of nitrogen, oxygen, methane; the pump laser includes any one of ultraviolet light, visible light, and infrared light.

9. The raman laser of claim 2, wherein the gas pressure regulating device comprises a gas cylinder; the gas cylinder is used for supplying Raman active gas into the wavelength converter.

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