CN102263359B

CN102263359B - Q-switched photonic crystal fiber laser

Info

Publication number: CN102263359B
Application number: CN201110168268A
Authority: CN
Inventors: 李松涛; 任芝; 李宁
Original assignee: North China Electric Power University
Current assignee: North China Electric Power University
Priority date: 2011-06-17
Filing date: 2011-06-17
Publication date: 2012-09-26
Anticipated expiration: 2031-06-17
Also published as: CN102263359A

Abstract

The invention discloses a Q-switched photonic crystal fiber laser. A Q switching device comprises a non-defective photonic crystal fiber and a modulator, wherein the modulator applies stress to the non-defective photonic crystal fiber to destroy the forbidden band structure of the photonic crystal fiber or change the forbidden band position of the photonic crystal fiber; and the non-defective photonic crystal fiber does not have any defect position in a three-dimensional periodical structure in a section.

Description

A kind of photonic crystal fiber Q adjusting optical fiber laser

Technical field

The present invention relates to a kind of photonic crystal fiber Q adjusting optical fiber laser, belong to the photoelectron technology field.

Background technology

Exist a kind of material of basis---photonic crystal in the photonic industry, the research of photonic crystal is not only the problem in the optical communication field, and it also will produce tremendous influence to other related industries simultaneously.Since Yablonowitch in 1987 and John have proposed the notion of photonic crystal and forbidden photon band respectively independently; Photonic crystal just becomes the hot subject that all receives very big attention both at home and abroad, has caused that in fields such as optical physics, Condensed Matter Physics, electromagnetic wave, information technologies people pay close attention to widely.In these short 20 years, photonic crystal is all being obtained significant achievement aspect theory research and the experimental study, and in some field certain application has been arranged also, such as photonic crystal PIC photon integrated circuit, photonic crystal optical waveguides, photon crystal filter etc.But this is a kind of completely new concept after all, and its research is goed deep into extensive not enough, and its a lot of characteristics are not also well used, and are necessary to carry out further research, especially aspect the realization and broadening in visible light wave range omnidirectional forbidden band.

Having a kind of in the photonic crystal is to be produced in the optical fiber, generally is referred to as photonic crystal fiber, and the general structure of photonic crystal fiber is shown in accompanying drawing 1 and accompanying drawing 2; It is a pore evenly arranged along the axial in optical fiber, sees from fiber end face, exists periodic two-dimensional structure; And one of them pore has suffered to destroy or disappearance, has so just produced defective, and light just can be propagated in defective; Defective wherein is shown in the middle body in accompanying drawing 1 and the accompanying drawing 2; In the central portion office, periodic two-dimensional structure has suffered to have destroyed, thus midway produced can leaded light defective.

Fiber laser is other a kind of very important device in the optoelectronic areas, and fiber laser comprises continuous wave laser and pulse laser, and is well-known; The generation of pulse laser generally needs Q switching; The employed adjusting Q crystal that generally all adopts of existing fiber pulse laser, the adjusting Q crystal of these types are generally all for original solid state laser designs, and it is complicated all to be accompanied by coupling when these Q switchings are applied to fiber laser; Structure is too fat to move; A series of problems that cost is high, thus make simple in structure that fiber laser itself had, advantage total loss such as with low cost.So be necessary to use a kind of advantage such as simple in structure, with low cost that can when realizing pulse laser output, keep that fiber laser itself had with the Q switching device that fiber laser simply is coupled.Prior art once proposed to use photonic crystal fiber as optical switch; But its switching characteristic utilization all is non-linear; Complicated on this nonlinear optical switch construction, there is certain difficulty in the modulation, so use this optical switch to have many drawbacks as the Q switching of fiber laser.The present invention proposes to this just, has designed a kind of simple in structurely, and modulation is convenient, is easy to the integrated photonic crystal fiber Q switching of fiber laser, and the fiber laser that comprises this Q switching.

Summary of the invention

The present invention proposes for addressing the above problem, and a kind of photonic crystal fiber Q adjusting optical fiber laser is provided, and well solves existing problem in the prior art.

Thinking of the present invention is at first to make a kind of flawless photonic crystal fiber; Let its forbidden band cover the gain bandwidth of fiber laser, let it be inserted in the resonant cavity of fiber laser, so then; Because the photonic crystal fiber of this moment does not have defective and has covered the gain bandwidth of fiber laser; The light that just makes it possible to produce gain can not produce vibration in the resonant cavity of fiber laser, use modulator that the photonic crystal that is inserted in the fiber laser is modulated then, thereby the periodic structure of periodically destroying said photonic crystal is destroyed its bandgap center position or the periodic bandgap center position that changes said photonic crystal; Like this; The light that is in the gain bandwidth just can periodically pass through said photonic crystal fiber, thereby in resonant cavity, produces vibration, produces pulse laser output.

The fiber laser that makes up with above-mentioned thought has simple in structure, with low cost, modulates advantages such as easy; Wherein employed Q-switching device be can with the photonic crystal fiber of the fine coupling of optical fiber; And employed photonic crystal fiber is flawless photonic crystal fiber, and it need not have complicated structure, only is that a photonic crystal fiber gets final product; Its modulation is also very simple, only needs applied stress or other influence powers to destroy or the bandgap center position that changes photonic crystal fiber can be realized.

The invention provides a kind of photonic crystal fiber Q adjusting optical fiber laser; Comprise: as the Fiber Bragg Grating FBG (FBG) of this fiber laser end mirror; Gain fibre as gain media; Pumping source gets into the fiber coupler of said gain fibre and Q-switching device with the optical coupling of pumping source; It is characterized in that; Said Q-switching device comprises zero defect photonic crystal fiber and modulator, and with forbidden band structure that destroys said photonic crystal fiber or the bandgap center position that changes said photonic crystal fiber, said zero defect photonic crystal fiber is meant and does not have any defective locations in the two-dimensional periodic structure in the cross section said modulator to zero defect photonic crystal fiber stress application.

According to fiber laser of the present invention, described modulator is the mechanical stress modulator.

According to fiber laser of the present invention, described modulator is ultrasonic stress modulation device.

According to fiber laser of the present invention, the ultrasonic stress that described modulator applied is adjustable, to control the output bandwidth of this fiber laser.

According to fiber laser of the present invention, but the length of said zero defect photonic crystal fiber is under the requirement of satisfying stress application, to select the shortest distance.

Description of drawings

Accompanying drawing 1 is the end view in kind of a photonic crystal fiber in the prior art;

Accompanying drawing 2 is end view of the structure of photonic crystal fiber in the prior art;

Accompanying drawing 3 is end view of the structure of employed zero defect photonic crystal fiber among the present invention;

Accompanying drawing 4 is structural representations of an embodiment of fiber laser of the present invention.

In above-mentioned accompanying drawing, d representes the diameter of photonic crystal fiber hollow pore, and Λ representes the structural constant of photonic crystal fiber; 1 expression fiber coupler, 2 expression pumping sources, 3 expression gain fibres; 4 expression photonic crystal fibers, 5 expression modulators, 6 and 7 represent FBG respectively.

Embodiment

Specify fiber laser of the present invention with embodiment below.

Attach Fig. 1 and 2 and show employed photonic crystal fiber in the prior art, as can be seen from the figure, in the photonic crystal fiber of prior art; Its inside exists defective, for example attaches shown in Fig. 1 and 2, and wherein the middle body at photonic crystal fiber lacks corresponding pore; Also promptly in central position; Its two-dimensional photon crystal structure has suffered destruction, thereby has produced defective in central position, makes that light can be in central position along Optical Fiber Transmission.Accompanying drawing 3 is employed photonic crystal fibers among the present invention; As can be seen from Figure 3; This photonic crystal fiber entreats the position not have any defective therein; But on whole cross section, form complete periodic two-dimensional structure, and promptly in this photonic crystal fiber, there is not defective locations, the light wave that also promptly is in this photonic crystal band can not be propagated along its length direction.The present invention has utilized this point exactly; This photonic crystal fiber directly is inserted in the resonant cavity of fiber laser; And make the forbidden band bandwidth of this photonic crystal fiber cover the gain bandwidth of fiber laser, under the situation that this photonic crystal is not affected, fiber laser can not produce vibration and form laser output owing to the influence of photonic crystal fiber so; But after receiving modulation effects, then can have high transmitance, thereby in resonant cavity, form vibration.

Fiber laser proposed by the invention is described on the basis that combines accompanying drawing 4 below; Fiber laser shown in the accompanying drawing 4; Comprise FBG6 and FBG7 as the fiber laser end mirror, pumping source 2 is used for the fiber coupler 1 with the optical coupling entering fiber laser resonant cavity of pumping source 2; The gain media gain fibre 3 of fiber laser, it also comprises zero defect photonic crystal fiber 4 that is serially connected in the fiber laser resonant cavity and the modulator 5 that this photonic crystal fiber 4 is modulated.

Modulator wherein can adopt the actuator to the photonic crystal fiber stress application; This actuator can be mechanical, also can be ultrasonic instrument, if mechanical actuator; Then this mechanical actuator can destroy the periodic structure in the photonic crystal fiber for after the photonic crystal fiber stress application; Thereby the forbidden band structure in the destruction photonic crystal fiber makes that the light in the gain bandwidth can pass through said photonic crystal fiber, thereby forms vibration; If the actuator of ultrasonic form; What then apply the change of ultrasonic photonic crystal fiber afterwards is exactly periodic structure; Can make promptly that also the bandgap center position of photonic crystal fiber is moved, thereby make light or the inner beam split of gain bandwidth in the gain bandwidth pass through said photonic crystal fiber.

The preferred actuator that adopts ultrasonic form; Because can be through accurate control applied ultrasonicly control the position that move in the forbidden band; Not only can realize pulse laser output, and can regulate the output bandwidth of laser to a certain extent, and with respect to mechanical stress; The actuating of ultrasonic form has the response time faster, can satisfy higher accent Q demand.

The length of said photonic crystal fiber preferably has less distance, and length should be not long, but its length is preferably selected the shortest distance, the long realization that will be unfavorable for transferring Q of length under the requirement of satisfying stress application.

Claims

1. photonic crystal fiber Q adjusting optical fiber laser; Comprise: as the FBG of this fiber laser end mirror; As the gain fibre of gain media, pumping source gets into the optical coupling of pumping source the fiber coupler of said gain fibre; And Q-switching device; It is characterized in that said Q-switching device comprises zero defect photonic crystal fiber and modulator, the forbidden band of said zero defect photonic crystal fiber covers the gain bandwidth of fiber laser; With forbidden band structure that destroys said zero defect photonic crystal fiber or the bandgap center position that changes said zero defect photonic crystal fiber, said zero defect photonic crystal fiber is meant and does not have any defective locations in the two-dimensional periodic structure in the cross section said modulator to zero defect photonic crystal fiber stress application.

2. fiber laser according to claim 1, described modulator are the mechanical stress modulator.

3. fiber laser according to claim 1, described modulator are ultrasonic stress modulation device.

4. fiber laser according to claim 3, the ultrasonic stress that described modulator applied is adjustable, to control the output bandwidth of this fiber laser.

5. fiber laser according to claim 1, but the length of said zero defect photonic crystal fiber is under the requirement of satisfying stress application, to select the shortest length.