CN201360098Y

CN201360098Y - Compact-type THz Raman optical fiber laser

Info

Publication number: CN201360098Y
Application number: CNU2009200226623U
Authority: CN
Inventors: 张玉萍; 张会云; 刘维慧; 王翠玲; 梁敏
Original assignee: Shandong University of Science and Technology
Current assignee: Shandong University of Science and Technology
Priority date: 2009-02-27
Filing date: 2009-02-27
Publication date: 2009-12-09
Anticipated expiration: 2019-02-27

Abstract

The utility model discloses a compact-type THz Raman optical fiber laser which comprises a pumping source, a coupling system and a metal coating hollow optical fiber, wherein the metal coating optical fiber core is filled with THz active gas, the front and the rear ends of the optical fiber are packed with sealing caps which are parallel to the end of the metal coating hollow optical fiber, the pumping source is a CO2 or N2O laser operated by radio frequency, and the coupling system is a CO2 or N2O laser lens group coupling system. The metal coating hollow optical fiber core with low wastage of the utility model is filled with low-pressure THz active gas, which is made into THz active optical fiber for replacing a heavy quartz tube or a container, an infrared laser pumping optical fiber generates THz wave, effective path of pumping light in the optical fiber is greatly increased, compared with a quartz tube or a container, the optical fiber with equal length has higher efficiency, as the optical fiber has the characteristics of light weight, small volume and flexibility, the whole set of the instrument is more compact and flexible.

Description

Compact THz Raman fiber lasers

Technical field

The utility model belongs to terahertz emission source technology field, is specifically related to a kind of fiber laser.

Background technology

In general, the wavelength of THz ripple is between 0.03mm～1mm, and the correspondent frequency scope is 0.3THz～10THz, is the electromagnetic radiation between millimeter wave and infrared light, is that last needs the wave band of research comprehensively in the electromagnetic spectrum.Because material has comprised abundant physics and chemical information in emission, reflection and the transmitted spectrum of THz wave band, therefore the THz ripple is in basic research fields such as physics, chemistry, astronomy, molecular spectrum, life and medical sciences, and all there are great scientific research value and wide application prospect in application study fields such as medical imaging, environmental monitoring, material tests, food inspection, radio astronomy, mobile communication, satellite communication and military radar.

At present, important basic problem comprises in the THz ripple research field: THz wave radiation source; THz ripple Detection Techniques; THz ripple self character and THz ripple and matter interaction.Wherein, the research to THz wave radiation source is the core research contents of THz technical field development in science and technology.The THz radiation source can be divided into two big classes according to the difference of mechanism of production: based on the THz radiation source of electronics with based on the THz radiation source of optics.THz radiation source based on optics mainly comprises: utilize ultrashort laser pulse to produce the THz radiation; Utilize nonlinear frequency transformation to produce the THz ripple; Produce THz lasing light emitter (being called for short optical pumping THz laser) based on the optical pumping gas molecule.With the immediate technology of the application be common optical pumping THz laser, it is to adopt the gas molecule in the infrared laser pumping generator to produce stimulated radiation formation THz laser, maximum average output power has reached 800mW (wavelength 118 μ m), light-light conversion efficiency is up to 0.727% (M.S.Tobin, A review of opticallypumped NMMW lasers, Proc.IEEE, 73 (1): 61-85,1985), and beam quality is better, and can export continually and steadily, and the maximum at present average output power of other optical means only is the microwatt magnitude, light-light conversion efficiency is less than 0.1%, so optical pumping THz laser is realizing having very big potentiality aspect the high power terahertz emission.What used at the mobile astronomical station of for example, setting up in the South Pole and carrying on satellite all is this optical pumping THz laser.The basic element of this laser is pumping source and THz ripple laser generator, advantage is, the beam quality of output is better, power output is higher, and can export continually and steadily, shortcoming is because THz ripple laser generator adopts thicker quartz ampoule or bulk container, only the length of THz ripple laser generating tube is generally more than 2 meters, diameter is about 30mm～50mm, can not be crooked, be difficult for moving, and the also huger heaviness of its bracing frame, it is very inconvenient to use, and has influenced the practical application area of optical pumping THz wave laser to a certain extent.

In recent years, people have also carried out THz ripple laser generator Miniaturization Research, mainly are that THz wave laser length is shortened, but shorten back THz signal relatively a little less than, do not reach instructions for use, be difficult to extensively promote at sciemtifec and technical sphere.

The utility model content

The purpose of this utility model provides that a kind of output beam quality is better, and power output is higher, and the THz Raman fiber lasers that can export continually and steadily and volume is little.

For achieving the above object, THz Raman fiber lasers of the present utility model is made up of pumping source, coupled system and optical fiber, wherein:

Described optical fiber is coat of metal gaseous core optical fiber, and it is the THz active gases that is filled with certain air pressure at coat of metal hollow fibre core, and requiring these active gasess is to absorb near the laser of 10 μ m (such as CO ₂Or N ₂The O laser) gas of generation THz wave band radiation, as, ammonia NH ₃Or fluoromethane CH ₃F etc. install sealing cap additional in coat of metal gaseous core optical fiber rear and front end, require the sealing cap termination parallel with the termination of coat of metal hollow-core fiber, and preceding sealing cap material has than high permeability infrared laser, as ZnSe or BaF ₂Or the NaCl wafer, back sealing cap material is infrared signal in the filtering effectively, and the THz ripple is had good permeability, as polytetrafluoroethylene (Teflon) or polyethylene, is used to export THz laser.

Described pumping source is the CO of radio frequency running ₂Or N ₂The O laser adds frequency selective element behind laser, as the rotating metallic grating, can realize the tuning output of THz ripple;

Described coupled system is an infrared laser set of lenses coupled system, and pump light is had transmitance more than 80%, and this set of lenses is with CO ₂Or N ₂The waist size and the angle of divergence of O laser are adjusted into suitable parameters, to improve pumping efficiency.

Operation principle of the present utility model is: infrared laser is coupled into the THz fiber core through coupled system, make fibre core activate gas generation population inversion, this process is followed more weak spontaneous radiation, the threshold value that surpasses Raman laser when pump power, fibre core activates in the gas, and stimulated Raman scattering will take place, and the THz ripple is strengthened in optical fiber after fiber-optic output is exported, and can pass through the pump light route selection, change the pumping light wavelength, thereby obtain the THz ripple output of wideband adjustable.

THz Raman fiber lasers of the present utility model charges into low pressure THz active gases in low-loss coat of metal gaseous core THz optical fiber, make the THz active fibre, replaces big and heavy quartz ampoule or bulk container, produces the THz ripple with the infrared laser pumping optical fiber.Because the reflex to pump light of optical fiber side, the active path of pump light in optical fiber increased greatly, compares with quartz ampoule or bulk container, and the optical fiber efficient of equal length is higher, and because optical fiber quality is light, volume is little and flexible characteristic, makes a whole set of instrument compacter, flexible.This THz fiber laser can room temperature running, tunable, good beam quality, conversion efficiency height, can make the THz ripple target location of going directly by optical fiber output, compact, flexible, robust, portable, the advantage of integrated optical pumping gas molecule laser and all solid state fiber laser is that other terahertz emission source is incomparable.The length of the utility model gaseous core optical fiber can be chosen according to the parameter of optical fiber and the relevant parameter of active gases, under the certain situation of in-core gas flow, and within the specific limits can be by the pressure of temperature controlled optical fiber method of temperature control in-core gas.

Description of drawings

Fig. 1 is an overall structure schematic diagram of the present utility model;

Fig. 2 is the sectional view of the utility model coat of metal gaseous core optical fiber;

Fig. 3 is sealing cap example structure figure before the utility model coat of metal gaseous core optical fiber;

Fig. 4 is the utility model coat of metal gaseous core optical fiber aerating device structure chart of bleeding.

Fig. 5 is the bleed assembling schematic diagram in when inflation of the utility model coat of metal gaseous core optical fiber.

Among the figure: 1-pumping source, 2-coupled system, 3-THz optical fiber, 4-THz ripple, the outer ducting layer of 5-, the 6-coat of metal, 7-gaseous core, the 8-gas container, 9-gas container plastic closures, 10-window, the 11-sealing compound, 12-plastics interface, 13-device cover, the 14-erection seat, 15-O grommet type seal, 16-sealing gasket, the 17-flange, 18-external screw thread, 19-internal thread.

Embodiment

As shown in Figure 1, the utility model comprises pumping source 1, coupled system 2 and THz optical fiber 3, and THz optical fiber 3 is made up of at the THz active gases that fibre core is filled with certain air pressure coat of metal hollow.

Among the embodiment, adopt the coat of metal optical fiber of internal diameter 2mm, charge into fluoromethane CH at fibre core under the normal temperature ₃F gas, with following method with optical fiber seal.Use Miniature RF CO ₂Or N ₂The O laser pumping, pump light is through CO ₂Or N ₂O laser lens group coupled system 2 enters optical fiber 3, activates in the gas at fibre core stimulated Raman scattering takes place, and can record THz ripple 4 at optical fiber 3 outputs, changes the pumping light wavelength, obtains THz ripple 4 outputs of wideband adjustable.

Above-mentioned coat of metal gaseous core optical fiber sectional view as shown in Figure 2, skin is outer ducting layer 5, ducting layer 5 is coated with the Au or the coats of metal such as Ag or Cu 6 outside, fiber optic hub is a gaseous core 7.

The structure of the preceding sealing cap of described coat of metal gaseous core optical fiber as shown in Figure 3, its structure is: it is that a side at a gas container 8 is provided with the port that inserts optical fiber 3, and gas container 8 is selected for use pumping laser is absorbed few ZnSe material; Port is provided with window 10, and window 10 is selected for use CO ₂The ZnSe material that the laser height sees through; The opposite side of gas container 8 is provided with the socket that inserts optical fiber, seals with sealing compound 11 behind the insertion optical fiber; The bottom surface of gas container 8 is connected with plastics mouth 9, and plastics mouth 9 is tightly connected with gas container 9; Sealing compound 11 seals optical fiber and preceding sealing cap.

Back sealing cap structure is identical with preceding sealing cap structure, and different is that gas container, plastic closures and window are all selected for use few polytetrafluoroethylene or the polyethylene of THz ripple absorption.

In order to realize finding time, inflate and sealing of coat of metal gaseous core optical fiber, specialized designs the aerating device of bleeding, this apparatus structure is as shown in Figure 4.It is made up of device cover 13, erection seat 14 and flange 17, device cover 13 is provided with internal thread 18, erection seat 14 is provided with the external screw thread 19 that cooperates with internal thread 18, device cover 13 is added with O grommet type seal 15 when being threaded with erection seat 14, erection seat 14 is added with sealing gasket 16 when being connected with flange 7, in addition, be provided with plastics interface 12 on device cover 13, device cover 13 forms air chamber.

Optical fiber is bled, inflated and the operation of carrying out contactless welder is a (see figure 5): at optical fiber 3 two ends sealing cap shown in Figure 3 is installed, is connected the aerating device of finding time respectively at the two ends of optical fiber then, be communicated with by optical fiber 3.By air pressure control optical fiber 3 internal gas pressures of control air chamber, realize bleeding and inflating by air chamber, carry out the contactless welding of laser by the plastics interface on the air chamber 12.Take off the sky aerating device after the welding, make THz optical fiber.Wherein bleed, inflation and contactless welding operation step be:

The first step: earlier sealing gasket 16 and flange 17 are installed on the optical fiber 3;

Second step: preceding sealing cap is loaded onto in optical fiber 3 terminations; With sealing compound 11 optical fiber and preceding sealing cap are tightly connected;

The 3rd step: before will being equipped with the optical fiber 3 of sealing cap be fixed to by flange 17 and sealing gasket 16 find time, aerating device seat 14, flange 17 is pushed down sealing gasket 16, make find time, 14 sealings of aerating device seat;

The 4th step: will find time, aerating device cover 13 by internal thread 19 and external screw thread 18 with find time, aerating device seat 14 is connected, middle usefulness O grommet type seal 15 seals;

The 5th step: the other end of optical fiber connects according to above-mentioned steps that another is found time, aerating device;

The 6th step: two find time, the interface 12 of aerating device is connected respectively to air exhauster and inflator, air is pumped into air pressure just charges into fluoromethane CH when low ₃F gas gas is taken out, is filled, and so forth several times, but gassy in the optical fiber then, and pressure 20～40mbar (1bar=10 of control gaseous ⁵Pa);

The 7th step: see through find time, aerating device cover plastics interface 12, with the method for the contactless welding of laser, with front and back sealing cap gas container plastics mouth welded seal;

The 8th step: lay down the aerating device of bleeding, obtain being filled with the THz optical fiber of required active gases.

Claims

1, a kind of compact THz Raman fiber lasers is characterized in that it is made up of pumping source, coupled system and optical fiber, wherein:

Described optical fiber is coat of metal gaseous core optical fiber, and it is to be filled with the THz active gases in coat of metal hollow-core fiber fibre core, installs ZnSe, BaF additional at coat of metal gaseous core optical fiber front end ₂Or NaCl wafer sealing cap, the rear end installs polytetrafluoroethylene or polyethylene sealing cap additional, requires the sealing cap termination parallel with the termination of coat of metal hollow-core fiber;

Described pumping source is the CO of radio frequency running ₂Or N ₂The O laser;

Described coupled system is CO ₂Laser lens group coupled system has transmitance more than 80% to pump light.

2, compact THz Raman fiber lasers as claimed in claim 1 is characterized in that, at CO ₂Be added with frequency selective element behind the laser.