CN100438237C

CN100438237C - Broad band TH2 light generator

Info

Publication number: CN100438237C
Application number: CNB2006101168109A
Authority: CN
Inventors: 徐世祥; 彭滟; 蔡华; 董华芳; 曾和平
Original assignee: East China Normal University
Current assignee: East China Normal University
Priority date: 2006-09-29
Filing date: 2006-09-29
Publication date: 2008-11-26
Anticipated expiration: 2026-09-29
Also published as: CN1988298A

Abstract

This invention relates to a super-quick optical technology including utilizing optical non-linear conversion technology in a laser cavity to generate THz laser, and said generator utilizes a non-linear optical rectification theory to put a THz laser generator at the beam waist in the cavity to increase its laser conversion efficiency. Since a laser oscillator is used as a pump source, the THz laser generated by non-linear optical rectification has the character of wide spectrum and high repeatability.

Description

Broad band TH 2 light generator

Technical field

The present invention relates to ultrafast optical technology aspect, its technological core is to produce thz laser with optical nonlinearity switch technology in the laser cavity.

Background technology

Far infrared or tera-hertz spectra district have attracted the increasing attentiveness of people owing to its nearly more than ten years of unique optical characteristics.Up to the present, the terahertz optics application study has been spreaded all over fields such as physics, chemistry, material, biomedicine, national defence, environment measuring, indicating development potentiality and using value that terahertz optics is huge, all can not underestimate the impetus of scientific research, national economy and social development.In many terahertz lights learned a skill, broadband Terahertz time-domain spectral technique (THz-TDS) (as shown in Figure 1) was wherein one of outbalance and commonly used technology.Based on the nonlinear optics rectification and be aided with the BALANCED measuring technique, make THz-TDS have simple, reliable and relatively inexpensive characteristics.Its typical structure comprises a cover femtosecond laser source and a pair of Terahertz emission and measurement mechanism through particular design.Be used at present to produce that the lasing light emitter of Terahertz light wave is common is femto-second laser oscillator or femtosecond laser chirped pulse amplification system.These two kinds of methods all produce thz laser outside laser cavity.The femto-second laser oscillator is as pumping and the detection light of THz-TDS, and its high pulse repetition frequency (general inferior 100MHz level) helps obtaining high signal to noise ratio when detecting with phase lock amplifying technology.Yet low pulse power causes the low non-linear conversion efficient of terahertz light, has reduced the signal to noise ratio of system from another approach.Femtosecond laser regenerative amplification system can increase substantially output laser pulse power, but its output pulse recurrence rate (general 1kHz level) is also much lower relatively, has increased the operating cost of whole system simultaneously.

Summary of the invention

The objective of the invention is according to above-mentioned the deficiencies in the prior art part, a kind of broad band TH 2 light generator is provided, this generator utilizes nonlinear optics rectification principle that the thz laser generator is placed in the laser cavity one place with a tight waist, improve the thz laser conversion efficiency effectively, solved problems of the prior art.

The object of the invention realizes being finished by following technical scheme:

A kind of broad band TH 2 light generator comprises ultrashort pulse laser oscillator, thz laser generator, it is characterized in that described thz laser generator is positioned at ultrashort pulse laser oscillator.

Described thz laser generator is positioned at a place with a tight waist of ultrashort pulse laser oscillator.

Described thz laser generator is placed with Brewster angle with respect to the ultra-short pulse laser in the laser oscillator.

Advantage of the present invention is owing to be that generation thz laser crystal is placed in the chamber, make full use of the characteristic of high light intensity in the laser cavity, thereby improve the thz laser conversion efficiency effectively; Owing to utilize laser oscillator as pumping source, the thz laser that utilizes the nonlinear optics rectification to produce has wide spectrum, tunable characteristic; It is the repetition rate height that laser oscillator also has an advantage as pumping source, helps using phase-locked measurement; Simple and compact for structure, easy to adjust, cost is low.

Description of drawings

Accompanying drawing 1 free space time-domain broadband Terahertz electro-optic sampling spectrometer;

Accompanying drawing 2 structural representations of the present invention;

The accompanying drawing 3a embodiment of the invention is used free space time-domain broadband Terahertz electro-optic sampling spectrometer architecture schematic diagram;

The accompanying drawing 3b embodiment of the invention is used free space time-domain broadband Terahertz electro-optic sampling spectrometer architecture schematic diagram.

Embodiment

Feature of the present invention and other correlated characteristic are described in further detail by embodiment below in conjunction with accompanying drawing, so that technical staff's of the same trade understanding:

Shown in Fig. 1,2,3a, 3b, symbol is described below among the figure:

As Fig. 1, L1～5 are lens, and P1, P2 are polarizer, and M1～9 are 45 ° of plane mirrors, BS1～3 are beam splitter, PM1～4 are 90 ° of off axis paraboloidal mirrors, and Ti:S is a titanium-doped sapphire, and TC is the Terahertz crystal, OE is that Terahertz detects crystal, D1, D2 receiver, S are sample, and NA is neutral attenuator.

As Fig. 2, L is lens, and P1, P2 are Brewster prism, and CR1, CR2, CR3 and CR4 are concave mirror, and PM is 90 ° of off axis paraboloidal mirrors, and Ti:S is a titanium-doped sapphire, and TC is the Terahertz crystal, and HR is 0 ° of plane high reflective mirror.

As Fig. 3 a, 3b, L is lens, and P1, P2 are Brewster prism, CR1, CR2, CR3 and CR4 are concave mirror, PM is 90 ° of off axis paraboloidal mirrors, and Ti:S is a titanium-doped sapphire, and TC is the Terahertz crystal, C is a phase compensator, M1～6 are 45 ° of high reflection mirrors, and P is a polarizer, D1, D2 receiver, S is a sample, and HR is 0 ° of plane high reflective mirror.

Present embodiment continuous green pumping laser gain media Ti doped saphire.Its laserresonator is by a plate plane high reflective mirror HR, and four concave mirror CR1～CR4 form optical resonator.Prism is used for dispersion compensation to P1, P2.This laser produces femtosecond light pulse output.Luminous power approaches 50 times of chamber external power in its corresponding chamber.By proper optical design, make to have one undersized (in the drawings between CR3 and the CR4) with a tight waist in the resonant cavity, and the crystal TC that will produce the Terahertz light wave places this with a tight waist locating with Brewster angle, thereby improve the conversion efficiency of Terahertz light wave greatly.Because the terahertz light wavelength that is produced is about 500 times of its pump light, so its angle of divergence is also greater than pump light.The anti-concave mirror CR4 of height is designed to small-bore, allows it can block pump light, can allow Terahertz light wave as much as possible overflow again from its edge.The Terahertz light wave that overflows is collected with one 90 ° of off axis paraboloidal mirrors.Because the diversity of thz laser much larger than pumping laser, is easy to collect the thz laser that is produced by the mode of space coupling.

As Fig. 3 a, 3b, present embodiment is applied in two kinds of structural representations in the Terahertz electro-optic sampling spectrometer of free space time-domain broadband.Utilize nonlinear optics switching process outside the chamber among present embodiment replacement Fig. 1 among the figure, the broadband thz laser that produces focuses on another electrooptic crystal behind two 90 ° of off axis paraboloidal mirrors, and the ultra-short pulse laser that spills from CR2 is focused on the electro-optic sampling crystal with the broadband terahertz light through a time delay line as surveying light.Survey light then and received by a BALANCED detector through a slice phase compensator and polarization beam apparatus, its output signal is transported to PC and handles behind a lock-in amplifier.Testing sample is placed between two 90 ° of off axis paraboloidal mirrors.This device can be used for the research in fields such as material science, medical science, environment measuring, atmosphere sensing.

Utilize present embodiment also to can be used for the many pumping probe experiments of terahertz light imaging.The broadband thz laser focuses on another electrooptic crystal behind four 90 ° of off axis paraboloidal mirrors, the ultra-short pulse laser that spills from CR2 is focused on the electro-optic sampling crystal with the broadband terahertz light through a time delay line as surveying light, thereby reaches the purpose of electro-optic sampling.This apparatus features is at second and the 3rd 90 ° of off axis paraboloidal mirror one focus point to be arranged at terahertz light, so also can be used for the research of terahertz light scanning imagery, Terahertz pumping-probe aspect.

Claims

1. broad band TH 2 light generator, comprise ultrashort pulse laser oscillator and the Terahertz crystal that is used to produce the Terahertz light wave, it is characterized in that described Terahertz crystal is positioned at a place with a tight waist of ultrashort pulse laser oscillator, and described Terahertz crystal is placed with Brewster angle with respect to the ultra-short pulse laser in the laser oscillator.