Stimulated Raman Scattering in Stimulated Raman Scattering in Crystals as the Basic for Creating of Crystals as the Basic for Creating of New All-Solid-State Laser SystemsNew All-Solid-State Laser Systems

基于创建中的新型全固态激光系统的晶体基于创建中的新型全固态激光系统的晶体中受激中受激 RamanRaman 散射散射

V.A.V.A. OrlovichOrlovich

B.I. Stepanov Institute of Physics,National Academy of Sciences of Belarus,

Nezalezhnasti Ave. 68, 220072, Minsk, Belarus

NANA-2010 / 1

ContentContent 内容内容1. Introduction: Stimulated Raman scattering as nonlinear optical effect

引言： SRC 的非线性光学效果

• Diode-pumped lasers with intracavity Raman conversion

具有腔内 Raman 转换的二极管泵浦激光器– Continuous-wave lasers 连续波激光器– Pulsed lasers 脉冲激光器

1. Pulsed nanosecond laser systems with Raman convertors 有 Raman 装换装置的脉冲十亿分之一秒激光系统

– Continuously tunable laser systems 连续可调节式激光系统– Pulsed NIR lasers 脉冲式 NIR 激光器– Pulsed visible and UV lasers 脉冲式可见及远红外激光器– Pulsed high average power and high repetition rate NIR lasers 脉冲式高均功率及高

重复率 NIR 激光器

• Eye-safe pulsed laser systems 对眼安全的脉冲式激光系统

• Conclusion 结论

NANA-2010 / 2

Spontaneous Raman Scattering (Raman effect)Spontaneous Raman Scattering (Raman effect)自发性自发性 RAMANRAMAN 散射（ 散射（ RAMAN RAMAN 作用）作用）

Raman scattering is inelastic process of light scattering. It involves in action the non-propagating Raman scattering is inelastic process of light scattering. It involves in action the non-propagating collective modes of the substance. collective modes of the substance. Raman 散射是光散射的无弹性进程。它包括无扩展收集式

NANA-2010 / 3

In the spontaneous regime of Raman scattering, the power of the Stokes and anti-Stokes waves is proportional to the power of the pumping wave. Raman 斯托克斯散射和反斯托克斯散射波的功率与泵浦波功率成比例

S = L -

L S

Las

as = L +

S L S L

Stokes scattering

斯托克斯散射

Anti-Stokes scattering

反斯托克斯散射

LPdP LS

~

LS PP 710~ WPL 1

differential cross

section of the Raman transition Raman 变换的微分交叉面

StimulatedStimulated RamanRaman ScatteringScattering (I)(I)受激受激 RamanRaman 散射散射

At Stimulated Raman Scattering (SRS):

• laser radiation power is > 1 kW; 激光放射能大于 1kw

• as a consequence the Stokes wave power increases; Stokes 波功率增加的推论• as a result : 结果

a) the internal vibration mode of the medium is driven by the interference of the pump and Stokes waves; 媒介内部振动模式是由 pump 和 stokes 波干涉所驱动

b) the Stokes wave is driven by the modulation of the pump wave by the material oscillations. 物质震荡调节的 pump 波驱动 stoke 波

NANA-2010 / 4

;exp0 1 zIgIzI SLSSS ;~ 1 SSSS IgIz

I

;505.2GW

cmg SRS arises at : ;1SLgI

g – Raman gain coefficientRaman 增益系数 Is ≤ IL

SRS: Field of InvestigationsSRS: Field of Investigations 研究领域研究领域General DirectionsGeneral Directions 总方向总方向

NANA -2010 / 5

FrequencyConversion

变频

PulseCompression

脉冲压缩

Beam Combining

光线合成

Femto- andattosecond

pulse generation

飞秒以及阿托秒脉冲

Micro Raman lasers (50 μm-size)

for microelectronics微电子器材的

微型 Raman 激光Raman fiber

lasersRaman 纤维激光

traditional

traditi

onal

trad

itio

nal

New

New

New

Raman solitonsin communications

通讯中的 Raman 孤立子

trad

itio

nal

Raman in solids

Raman 在固体中

New

SRSSRS

DirectionsDirections ofof investigationsinvestigations 研究方向研究方向 Measurement of nonlinear-optical parameters of Raman crystals and determination

of its most perspective application areas (methods of the Raman amplification, z-scan). Raman 水晶中非线性光学参数测量以及其最具可能的应用领域

Elimination of the self- and cross interaction effects at SRS excitation with short (pico- and femtosecond) laser pulses. 用短激光脉冲激发 SRS 放射自己和相互作用

Investigation of the physical processes in intracavity Raman conversion in end-diode pumped microchip and minilasers. 终极二极管泵浦芯片及微激光在腔内 Raman转换的物理过程的研究

Investigation of the thermal effects in crystal Raman lasers 在晶体 Raman 激光中热效应的研究

Development of methods of sharp reducing (up to ~ 103) of the Raman laser threshold. Raman 激光临界的急剧减少 ( 至 ~103) 方法的发展Results of our physical researches on the above directions will not be stated in the report. The main attention will be concentrated on Raman convertors and Raman lasers investigated by us. 上述方式的物理研究结果将不会在报告中陈述。我们主要致力于 Raman 转换器及 Raman 激光的研究

NANA -2010 / 6

NANA -2010 / 7Diode-Pumped Lasers with Intracavity Raman ConversionDiode-Pumped Lasers with Intracavity Raman Conversion

具有腔内 Raman 转换的二极管泵浦激光器 Continuous Wave (CW) GenerationContinuous Wave (CW) Generation

连续波生成连续波生成Continuous wave (CW) lasersare widely used in: 持续波激光广泛应用于：• atomic and molecular spectroscopy 原子及分子光谱学• medicine 医药• environmental control 环境控制• optical communications 光学通信• instrumentation 仪表

At the time being only a small number of CW lasers generating of few fixed frequencies or wavelength-tunable in the limited visible and infrared spectral ranges are available. 目前仅在少数的固定频率或又显得可见光和红外光谱范围的 CW 激光生成，是可用的

We have developed CW crystalline Raman lasers firstly in the worldWe have developed CW crystalline Raman lasers firstly in the world世界上我们首先开发的世界上我们首先开发的 CWCW 晶体晶体 RamanRaman 激光激光

The theory of such lasers is presented in the following papers:该激光理论已经发表在下列论文中：1. V.A. Lisinetskii, A.S. Grabtchikov, P.A. Apanasevich, M. Schmitt, B. Kuschner,S. Schlucker, and V.A. Orlovich. J. Raman Spectr.37 (2006) 4212. V.A. Lisinetskii, D.N. Busko, R.V. Chulkov, A.S. Grabtchikov, P.A. Apanasevich,V.A. Orlovich. J. Appl. Spectroscopy 75 (2008) 284

The results of our experiments are stated in the papers:我们的试验结果陈述在这些论文中： Opt. Lett. 29 (2004) 2524; Opt. Lett. 30 (2005) 1701; Laser Phys. Lett. 3 (2006) 71; Appl. Phys. B 88

(2007) 499; Appl. Phys. B 86 (2007) 511.

Our approach for Our approach for CW Raman laserCW Raman laser 我们的我们的 CW RamanCW Raman 激光研究方激光研究方法法

NANA -2010 / 8

Using of Raman crystals- Hydrogen G 2.5 cm/GW; barium nitrate G = 48 cm/GW

1. Accumulation of Stokes radiation in independent Raman laser 独立 Raman 激光中 Stokes 放射的积聚

pump

StokesLaser Raman

2. Accumulation of pump and Stokes radiation at intracavity Raman conversion 腔内 Raman 转换泵浦和 Stokes 放射的积聚

3. Accumulation of pump and Stokes radiation at intracavity self-frequency Raman conversion

腔内自频 Raman 转换中泵浦和 stokes 放射的积聚

Laser Raman

pump

Stokes

pump

StokesLaser Raman

4. Accumulation of pump and Stokes radiation at intracavity Raman conversion in composite crystals 合成晶体中腔内 Raman 转换中的泵浦和 Stokes 放射的积聚

pumpRaman

pump

Stokes

NANA -2010 / 9

Stokes (1181 nm)

Laser (1067 nm)

Laser diode (808 nm)

fiber

Nd:KGW or Nd:YVO4 crystals

Cavity腔

Intracavity Raman self-frequency conversionIntracavity Raman self-frequency conversion in CW end-diode-pumped lasers in CW end-diode-pumped lasers

在在 CWCW 终极二极管泵浦激光内的腔内终极二极管泵浦激光内的腔内 RamanRaman 自频率转换自频率转换(optical(optical scheme) scheme) 光学计划光学计划

Raman self-frequency conversion implies

that the processes of laser generation and

Raman conversion occur in one and the

same crystal

Raman 自频率频转换意味着产生激光和 Raman

转换在同一晶体中处理

NANA -2010 / 10

Intracavity Raman self-frequency conversion at Intracavity Raman self-frequency conversion at high power end-diode-pumpinghigh power end-diode-pumping 在高能终极二激光在高能终极二激光

泵浦中的腔内泵浦中的腔内 RamanRaman 自频率转换自频率转换

Points are experimental data. Solid lines are mathematical simulation data at the different intracavity losses (1 - 0.0032; 2 - 0.0047; 3 - 0.0062 (the best approximation); 4 - 0.0077; 5 - 0.0091). Crystal length is 12 mm. 点是试验数据。实心线条是在不同腔内损失的数学仿真。

0 5 10 15Pump,W0.0

0.5

1.0

1.5

2.0

2.5

3.0

Stokes output

power,W1

2

3

4

5

Nd:YVO4 / YVO4

NANA -2010 / 11

2 4 6 8 10 12 14 16 18 20 22 240.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2 Fundamental Stokes Yellow

Ou

tpu

t po

we

r, W

Pump power, W

Intracavity Raman self-frequency Intracavity Raman self-frequency conversion and coherent mixingat high conversion and coherent mixingat high

power power end-diode-pumpingend-diode-pumping 在高功率终极二极管在高功率终极二极管泵浦上腔内泵浦上腔内 RamanRaman 自频转换和连贯混合自频转换和连贯混合

Stokes 1176 nmFundamental 1064 nm Sum-mixing 559 nm

Beam profiles near the waist腰部附近的光线轮廓

NANA -2010 / 12

Since 1987, much efforts were made to investigate and create diode pumped microchip lasers. 自 1987年，许多成就产生于二极管泵浦微芯片激光的研究和创造

Input mirror

Output mirror

Diode pump

Output

Gain medium

Actively or passively

Q-switched devices

DDiode-iode-PPumped umped Pulsed LPulsed Lasersasers with Iwith Intracavity Rntracavity Raman aman ConversionConversion 具有腔内具有腔内 RamanRaman 转换的二极管泵浦脉冲式激光器转换的二极管泵浦脉冲式激光器

The microchip lasers with passive

Q-switching can generate pulses

with a duration from 0.2 ns to 8 ns

and a peak power up to dozens of

kilowatts 有无源 Q 开关的微芯片激光器可以产生脉冲，其持续力可达 0.2 ns 到 8 ns ，高峰电流可达数千瓦

A typical cavity length is some millimeters. 特有的腔长大约是几毫米A single frequency mode of generation 产生单频率模式

NANA -2010 / 13

The advantages of intracavity pulsed Raman

conversion are:

腔内脉冲式 Raman 转换的优点：- a low threshold of Raman

excitation; 激活 Raman 的低临界值- the possibility of the pump and

Stokes pulse duration control

(including pulse compression) 泵浦及 Stokes

脉冲持续时间的可控制控制性（包括脉冲压缩）

Actively or Passively Q-switched devices

Input mirror

Raman medium

Gain medium Output mirror

DDiode-iode-PPumped umped Pulsed LPulsed Lasersaserswith Iwith Intracavity Rntracavity Raman Conversionaman Conversion

We have developed diode-pumped microchip- and mini-lasersWe have developed diode-pumped microchip- and mini-laserswith intracavity Raman conversion firstly in the world.with intracavity Raman conversion firstly in the world. 我们首先在世界上开发了具我们首先在世界上开发了具

有腔内有腔内 RamanRaman 转换的二极管泵浦微芯片和微激光转换的二极管泵浦微芯片和微激光

Our main publications: Our main publications: Appl. Phys. Lett. 75 (1999) 3742; J. Alloys and Compounds 300-301(2000)300; Appl. Phys. B 19 (2002) 113; Apl. Phys. Lett. 81 (2002) 2926; Appl. Phys. B (2003); JOSA B 22 (2005) 2450; Opt. Comm. 263 (2006) 52; Opt. Comm. 281 (2008) 5202; JOSA B, 2010 (in press)

-2 -1 0 1 2

0,00

0,02

0,04

0,06

0,08

0,10

8,91W

Am

pl

Time, ns

2nd Stokes 1st Stokes Laser

NANA -2010 / 14

Typical oscillograms of the output Stokes pulses from microchip laser with intracavity Raman conversion从腔内转换微芯片激光器输出 Stokes 脉冲的典型

示波图

48.5 ps

a)

221.8 ps

b)

Pp = 30kWPp = 40kW

DDiode-iode-PPumped umped Pulsed LPulsed Lasersaserswith Iwith Intracavity Rntracavity Raman Conversionaman Conversion

PP=8.9 W

NANA -2010 / 15

DDiode-iode-PPumped umped Pulsed LPulsed Lasers asers with Iwith Intracavity Rntracavity Raman conversionaman conversion

Additional nonlinear optical conversion (harmonic generation and sum-frequency mixing the radiation of microchip lasers)增加非线性光学转换（谐波产生及和频混合了微芯片激光器放射）

N Nonlinear-optical process 非线性光处理

Wavelength, nm

Output wavelength, nm

1 R = - , Raman generation

1196 1196

2 , Laser generation 1063 1063

3 R + R = 2 - 2 1196 + 1196 598

4 R + = 2 - 1063 + 1196 563

5 + = 2 1063 + 1063 532

6 2R + R = 3 - 3 598 + 1196 399

7 2R + = 3 - 2 598 + 1063 383

8 2R + 2R = 4 - 4 598 + 598 299

9 (2 - ) + (2 - ) = 4 - 2

563 + 563 282

10 2 + 2 = 4 532 + 532 266

11 (4 - 4)+ R =

5 - 5

299 + 1196 239

The wavelengths of the generated

radiation产生辐射的波长

= 9407 cm-1; R = 8360 cm-1; = 1047 cm-1

Pulsed nanosecond laser systems with Raman converters.Pulsed nanosecond laser systems with Raman converters.Continuously tunable laser systemContinuously tunable laser system 具有具有 RamanRaman 转换器的脉冲式十亿转换器的脉冲式十亿

分之一秒激光系统 连续可调的激光系统分之一秒激光系统 连续可调的激光系统

NANA -2010 / 16

Master oscillator - power amplifier (MOPA) Ti:Sapphire laser system

The system includes Nd:YAG laser, master oscillator - power amplifier (MOPA) Ti:Sapphire laser, LiF2

- - laser, harmonic generators and Raman convertor on Ba(NO3)2 crystal (Opt. Commun. 218 (2003) 351; J. Raman Spectr. 31 (2000) 851). 系统包括： Nd ： YAG 激光，主振荡器 - 功放， Ti ： Sapphire 激光， LiF2 激光，谐波发生器， Raman 转换器 在 BaNO3)2 晶体上

NANA -2010 / 17

Wavelength, nm

700 800 900 1000

En

erg

y,

mJ

0

20

40

60

80

Second Harmonic

Wavelength, nm300 350 400 450 500 550

En

erg

y,

mJ

0

10

20

30

40

Fourth Harmonic

Wavelength, nm

180 200 220 240 260

En

erg

y,

mJ

0

1

2

3

4

Third Harmonic

Wavelength, nm

200 220 240 260 280 300 320 340

En

erg

y,

mJ

0

2

4

6

8

10

Tuning curvesTuning curves调整调整曲线曲线

of MOPA Ti:Sapphire laser system (the fundamental, 2nd, 3rd, and 4th harmonics) for three different holographic selectors

针对三个不同的全息分离器

NANA -2010 / 18

Wavelength, nm

200 400 600 800 1000 1200 1400 1600 1800

En

erg

y, m

J

0.01

0.1

1

10

100

Optical scheme and tuning curves of continuously tunable Optical scheme and tuning curves of continuously tunable (187 - 1800 nm) pulsed laser system(187 - 1800 nm) pulsed laser system 光计划和连续可调脉冲式激光计划和连续可调脉冲式激

光系统的可调曲线（） 光系统的可调曲线（）

Pulsed High Energy NIR Raman LasersPulsed High Energy NIR Raman Lasers

脉冲式高能 NIRRaman 激光器 1st Stokes generation (1197 nm)

0 50 100 150 200 250 300

0

20

40

60

80

100

120

140

160

Four mirrors

Three mirrors

1st

Sto

kes

en

erg

y, m

J

Pump energy, mJ

Energy of 156 mJ is achieved

Efficiency - 59% (quantum efficiency - 66%)

NANA -2010 / 19

We have developed a Raman laser generating at three Stokes lines with record values of pulse energy (Opt. Comm. 272 (2007) 509). The problem of suppression of generation at higher Stokes lines has been solved. 我们已经开发了在三条具有脉冲能量记录值的 Stokes 线的 Raman 激光生成。已经解决了在较高的 Stokes 线上生成的抑制问题。

Pump

Inputmirror

Bariumnitrate(7 cm)

OC1

1st Stokes

2nd Stokes

M1

2nd Stokes

Pulsed High Energy NIR Raman lasers.Pulsed High Energy NIR Raman lasers.3rd Stokes generation (1599 nm)

Pump

Inputmirror Barium

nitratesOC3

3rd Stokes

OC3: HR at pump HR at 1st Stokes HR at 2nd Stokes R=35% at 3rd Stokes

To generate 3rd Stokes the 4th Stokes should be suppressed. But in barium nitrate crystal there is an absorption at 4th Stokes wavelength. So there is no necessity for additional 4th Stokes suppression and the simple linear cavity can be used 。 4thstokes 压缩后可产生 3rdstokes 。但是在硝酸钡晶体中， 4thstokes 波长被吸收。因此没有必要做额外的 4th stokes 压缩，简单的线性腔就可以被使用

Energy of 116 mJ is achieved

Efficiency - 42% (quantum efficiency - 63%)

NANA -2010 / 20

Pulsed Visible and UV Raman lasersPulsed Visible and UV Raman lasers脉冲式可见和紫外线脉冲式可见和紫外线 RamanRaman 激光器激光器

Quantum efficiency - 70%

40 60 80 100 120 1400

2

4

6

8

10

12

14

Out

put e

nerg

y, m

J

Pump energy, mJ

= 281 nm

20 40 60 80 100 120 1400

20

40

60

80

100

Sto

kes

ener

gy, m

J

Pump energy, mJ

= 563 nm

NANA -2010 / 21

This Raman laser with second harmonic generator is used in troposphere ozone lidar 此 2 谐波制造器的 Raman 激光被用作对流层臭氧激光雷达

To suppress the generation at 2nd Stokes line we have used three-mirror scheme for Raman laser cavity. Raman laser was based on Ba(NO3)2 crystal.

要压缩 2nd stokes ， 我们在 Raman 激光腔里用了三反射镜。 Raman 激光是以硝酸钡晶体为基础的

NANA -2010 / 22

Remote sensing of atmosphere by means of space-based lidars requireslaser sources with high average power. We have developed a Raman laser

with a record values of average power for a such application 用宇宙用途的激光雷达来实现的宇宙遥控感知需要有高均功率的激光源。 我们开发了用于此研究的有记录值的高均功率的 Raman 激光

(V.A. Lisinetskii, T. Riesbeck, H. Rhee, H.J. Eichler, and V.A. Orlovich, “High average power generation in barium nitrate Raman laser ”, Applied Physics B, published online November 1, 2009).

Repetition rate: ~1 kHzPulse duration: ~40-50 ns (FWHM)Generation bands:

1 Stokes: 1.197 m2 Stokes: 1.369 m3 Stokes: 1.598 m

Spectral bandwidth: 0.1-0.3 cm-1Beam divergence: <5 mradBeam quality factors:

1 Stokes: M2~32 Stokes: M2<23 Stokes: M2<5

Pulsed high average power and high repetition ratePulsed high average power and high repetition rateNIR lasersNIR lasers 脉冲式高均功率和高重复率脉冲式高均功率和高重复率 NIRNIR 激光器激光器

NANA -2010 / 23

0 10 20 30 40 50 60

0

3

6

9

12

15

18

Pou

t / Pp , %

Pou

t , W

Pp , W

0

5

10

15

20

25

30

0 10 20 30 40 50 60

0

3

6

9

Pou

t / Pp , %

Pou

t , W

Pp , W

0

3

6

9

12

15

18

0 10 20 30 40 50 60

0

1

2

3

4

5

6

Pou

t / Pp , %

Pou

t , W

Pp , W

0

2

4

6

8

10

The dependences of average output power Pout and conversion efficiency Pout/ Pp

on average pump power Pp

在平均泵浦功率上平均输出功率和转换效率的依赖性1st Stokes line

PPMAXMAX=17 W=17 W PPMAXMAX=9.5 W=9.5 W PPMAXMAX=5 W=5 W

2nd Stokes line 3rd Stokes line

Pulsed high average power and high repetition rate Pulsed high average power and high repetition rate NIR lasersNIR lasers

NANA -2010 / 24

Frequency doubling and coherent mixing of the radiation of the generated Stokes components is realized in BBO, LBO, and LiIO3 crystals to obtain the radiation in UV region. The radiation at 281.7, 290.3, 299.4, 309, 319.4, 330.4, 342.3, 368.7, 399.5, and 436 nm with average power from several mW to 20 mW has been generated.为了获得红外线区域的放射，我们实现了在 BBO ， LBO 和 LiIO3 水晶中由不断倍化及持续混合已产生的 stokes合成的放射。此放射在 281.7, 290.3, 299.4, 309, 319.4, 330.4, 342.3, 368.7, 399.5, and 436 nm给以 several mW to 20 mW 的均功率可以产生

The studied laser system allows one to generate the quasi-CW radiation at 21 wavelengths in the range of 281 - 1600 nm. Average power is varied from several mW to 1.2 W. Minimum spectral width of the radiation is equal to 0.2 cm-1.研究的激光系统考虑一个在 21 波长上 281-16000nm 范围内产生拟 -CW辐射。平均功率从几个MW 到 1.2W 不等。辐射的最小光谱宽度等于 0.2cm

Multiwave high repetition rate UV - NIR lasersMultiwave high repetition rate UV - NIR lasers多波高重复率多波高重复率 UV-NIRUV-NIR 激光器激光器

Maximum

Power (W)

Conversion efficiency

(%)

Raman threshold

(W)

Beam Quality Factor

Pulse Width

(ns) Pump, 532 nm

3.5 10.7 105

1st Stokes 563.4 nm 0.690 20.3 0.470 6.5 82

2nd Stokes 598.7 nm

1.190 35.3 0.300 6.5 73

3rd Stokes 638.7 nm

0.600 18.7 0.325 5.2 58

4th Stokes 684.5 nm

0.220 7 0.290 14.7 83

5th Stokes 737.3 nm

0.400 11.5 0.415 5.7 57

6th Stokes 799.0 nm

0.190 5.7 0.390 2.5 50

Pump, 1064 nm

3.9 - - 17.8 130

1st Stokes 1197 nm 0.630 16 0.620 6.2 95

2nd Stokes 1369 nm

0.405 10 0.710 6 65

3rd Stokes 1599 nm

0.310 5 0.720 5.6 45

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Eye-safe pulsed laser systemsEye-safe pulsed laser systems 对眼安全的脉冲式激光系对眼安全的脉冲式激光系统统

Eye-safe lasers find wide application in environmental protection, laser range-finders, lidars used in built-up areas.

There are two main approaches to obtain generation in eye-safe spectral range: 对眼安全激光器在环保，激光测距仪，用于建筑区域的激光雷达上有广泛的应用。有两个主要方法来获得对眼安全光谱范围内的生成。1. direct generation in crystals and glasses doped by erbium ions; 在加入铒离子的晶体和玻璃里直接产生

2. nonlinear optical conversion of radiation of lasers based on

neodymium-doped crystals. 在加入钕的晶体中进行激光器放射的非线性光学转换

We have investigated in detail the second approach. At the beginning we used lasers with lamp pump in our experiments. At present we use side-diode-pumped lasers. Nonlinear optical conversion was being obtained by Stimulated Raman Scattering in crystals and Optical Parametric Oscillation.我们主要对第二种方法进行研究。起初我们在试验中用带有 lamp 泵的激光。现在我们用二极管激光器侧泵激光器。 通过在晶体中的受激 Raman 散射及光参量振荡，我们得到了非线性光学转换。Our results are published in the following papers:

J. Opt. Technol. 67 (2000) 64; J. Appl. Spectr. 73 (2006) 254; J. Appl. Spectr. 73 (2006) 330; J. Appl. Spectr. 73 (2006) 535;J. Appl. Spectr.75 (2008) 516; J. Appl. Spectr. 76 (2009)499;J. Appl. Spectr. 76 (2009) 725; J. Appl. Spectr. 77 (2010) in press.

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Eye-safe pulsed laser systems based on Raman conversionEye-safe pulsed laser systems based on Raman conversion 基基于于 RamanRaman 转换的对眼安全脉冲激光系统转换的对眼安全脉冲激光系统We have used two approaches:We have used two approaches:

我们使用了两种方法我们使用了两种方法1. Laser generation was obtained in Nd:KGW crystal at work transition 4F3/2→4I13/2

在 Nd ： KGW 晶体里的转换工作中获得激光器生成。 λλ = 1.351 = 1.351 μμmm 。。a) this radiation excited SRS in laser crystal Nd:KGW (Raman self-frequency conversion)

该辐射激活在激光晶体 Nd ： KGW里的 SRS （）。 1.351 1.351 μμm → 1.538 m → 1.538 μμm.m.

b) this radiation excited SRS in additional Raman laser based on KGW crystal

该辐射激活基于 KGW 晶体的附加 Raman 激光器里的 SRS 。 1.3511.351 μμm → 1.538 m → 1.538 μμm.m.

Nd:KGW Nd:KGW1) 1.538 m (R =901.5 см-1 )

2) 1.507 m (R =767.5 см-1 )=1.351 m

Q-switch

=1.351 m

1St = 1.538 m

Q-switchNd:KGW

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Eye-safe pulsed laser systems based on Raman conversionEye-safe pulsed laser systems based on Raman conversion

Laser generation was obtained in Nd:KGW crystal at work transition 4F3/2→ 4I11/2 (λ = 1.067 μm).

This radiation excited three Stokes lines in Nd:KGW crystal

Nd:KGW Nd:KGW

Q-switch

3St=1.5 m

=1.067 m

1066 1068 1070 1498 1500 , nm

Laser output 3-rd Stokescomponets

Optical spectra around 1 and 1.5 m; the extreme positions of Raman line are shown.1 和 1.5um左右的光谱

。显示了 Raman 线的末端位置

1.067 m

1.5 m10 ns/div

Oscilloscope traces of the primary laser radiation and of the pulse

in the third Stokes component 初始激光放射的示波器和第三 Stokes组件里的脉冲图形

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Eye-safe pulsed laser systems based on OPOEye-safe pulsed laser systems based on OPOКТР- crystal-based OPO

1.06 m 1.57 m

Multimode Nd-laser

5,0 5,5 6,0 6,5 7,0 7,5 8,0

10

20

30

Ep, J

ЕS, mJ

1570 1571 1572 , nm

Output energy of OPO at eye-safe wavelength ~1.57 µm as a function of electrical pumping energy of Nd:YAG laser and optical spectrum around 1.57 m OPO 的输出能量在对眼安全波长 ~1.57 µm 作为 Nd:YAG 激光的电泵浦能量的功能和光学频谱 1.57 µm左右

Behavior of eye-safe radiation energy for prolonged source operation at frequency 10 Hz and histogram of relative frequencies hi = ni /ni for impingement of pulse energy Es in the i-th interval of 0.2 mJ; ni is the number of OPO pulses in the i-th interval.针对在频率 10Hz 的长期源操作对眼安全辐射能量的性能相关频率的直方图 hi = ni /ni 对脉冲能量的影响， Es 在0.2mJ 的第 i-th区间内， ni 是 OPO 脉冲在第 i区间数

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type laser channel of conversion output radiation

I. Nd3+:KGW(4F3/2 4I13/2 ): {SRS} I Stokes component

II. Nd3+:KGW(4F3/2 4I11/2): {SRS} III Stokes component

III. Nd3+:YAG(4F3/2 4I11/2): {OPO} signal wave

Eye-safe radiation sources on the basis of nonlinear optical conversion of diode-pumped laser radiation are in a stage of investigations. 在 二 极 管 泵 浦 激 光辐射 的 非 线 性 光 转 换 的 基础上 对 眼 安 全辐射源处 于 研 究阶段。 The prospective laser parameters are: pulse rate – 10-20 Hz, pulse energy – 30-50 mJ.未来的激光参数为：脉冲频率 - 10-20Hz ，脉冲能量 - 30-50mJ 。

Types of eye-safe radiation sources and Types of eye-safe radiation sources and

their main parameterstheir main parameters

对眼安全辐射源的类型和它们的主要参数对眼安全辐射源的类型和它们的主要参数

Type of conversion

Modulation regime 调制制度 Up, J ЕL,

mJ tL, ns , μm

86.5 mrad

f, Hz

Passive Q-switch (YAG:V3+)

8-11 9-13 15-25 1.538 13 1 Raman self frequency

conversion Electrooptical Q-switch (LiNbO3)

8 12 ~5 1.538 7 1 I

Extracavity腔外

Electrooptical Q-switch (LiNbO3)

9 10 ~5 1.538 1.507

- 1

intracavity 6 13.5 3 1.5 9 1

II extracavity 6 10.5 5-9 1.5 10 1

III extracavity 8 30 10 1.57 7 12.5

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ConclusionConclusion

1. Stimulated Raman Scattering in crystals is an efficient way for development laser systems generating the continuous wave radiation, as well as the pulse one with a pulse rate up to 100 kHz and a pulse width up to tens of femtoseconds; 晶体中的受激 Raman 散射是开发连续波辐射生成激光系统的有效途径，以及一脉接一脉率高达100kHz 和脉冲宽度达到几十飞秒；

2. The efficiency of laser radiation conversion into a single line defined in advance is more than 50 %; 在激光辐射转换成预先定义的单线的效率超过 50 ％ ;

3. Using intracavity Raman conversion it is possible to compress pulses at simultaneous increasing their peak power about ten times;使用内腔 Raman 转换有可能在同步压缩脉冲增加十倍左右的峰值功率

4. On the basis of SRS it is possible to develop simple and compact laser systems for different applications, including the systems generating in eye-safe spectral range.在 SRS 的基础上针对不同的应用，包括对眼安全光谱范围内生成系统，可以开发简单和复杂激光系统。

Our scientific group has a great experience in laser Our scientific group has a great experience in laser

physics, nonlinear optics, laser spectroscopy, as well physics, nonlinear optics, laser spectroscopy, as well

development of laser and optical systems for practical development of laser and optical systems for practical

applications (environmental protection, medicine, applications (environmental protection, medicine,

scientific research et set ).scientific research et set ).

我们的科学团队在激光物理，非线性光学，激光光谱学等领我们的科学团队在激光物理，非线性光学，激光光谱学等领域以及激光和光学实际应用（环境保护，医学，科学研究等域以及激光和光学实际应用（环境保护，医学，科学研究等等）系统的开发具有丰富的经验。等）系统的开发具有丰富的经验。

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Our Scientific GroupOur Scientific Group

Thank you for attention !Thank you for attention !