Recent Advances in Solid State Lasers and Nonlinear Optics for Remote Sensing Peter F. Moulton Q-Peak, Inc. Lidar Remote Sensing for Industry and Environment Monitoring III (Conference 4893) SPIE s Third International Asia-Pacific Environmental Remote Sensing Symposium 2002 Hangzhou, China October 25, 2002
Outline Ti:sapphire lasers for UV-based sensors NASA Langley Alex Dergachev, Bhabana Pati High-energy OPO for aerosol sensing NASA Langley Glen Rines Tandem OPO for infrared DIAL AFRL Yelena Isyanova Other efforts
Ti:sapphire absorption and gain spectra 7.E-20 3.5E-19 6.E-20 3E-19 Absorption cross section (cm2) 5.E-20 4.E-20 3.E-20 2.E-20 2.5E-19 2E-19 1.5E-19 1E-19 Gain cross section (cm2) 1.E-20 5E-20 0.E+00 0 400 500 600 700 800 900 1000 1100 Wavelength (nm)
Laser-pumped, pulsed Ti:sapphire laser combines high energy and high beam quality Pump #1 Ti:sapphire crystals Output Prisms Pump #2 GRM HR Gain-switched operation, similar to Q-switched Nd lasers
Pulsed Ti:sapphire input-output, 727-960 nm Ti:sapphire output energy (mj) 500 450 400 350 300 250 200 150 100 50 790 nm 727 nm 911 nm 960 nm 0 0 200 400 600 800 1000 1200 1400 Green pump energy (mj)
LASE system with Ti:sapphire laser has measured global water-vapor profiles
Harmonic conversion of Ti:sapphire lasers for species sensing Harmonic 4th NO 3rd Benzene Toluene Ozone Cl2 Hg SO2 2nd NO2 700 750 800 850 900 950 Wavelength (nm)
Block diagram of ozone lidar transmitter SLM Diode Laser - On-Line Seeder SLM Diode Laser - Off-Line Seeder Dichroic Mirror Isolator Double-Pulse Lamp Driver BBO- or LBO-based Passive SHG Module Pulsed Ti:sapphire Unstable-Resonator Laser CLH Nd:YLF Pump Laser Passive THG Module Double-Pulse UV Output
THG efficiency and energy exceeded 45% and 30 mj THG Efficiency 50 45 40 35 30 25 20 15 10 5 0 50 45 40 35 30 25 20 15 10 5 0 0 10 20 30 40 50 60 70 80 Input Energy (mj) THG Output Energy (mj)
High-energy OPO for eye-safe aerosol sensing
Compact Nd:YAG/YLF laser head (CLH)
Laser performance with Nd:YLF and KTP/KTA OPO angle tuning 1053-nm Output (mj) 800 600 400 200 10 Hz 20 Hz 30 Hz M 2 = 10-15 0 0 20 40 60 80 Lamp Energy (J) 2.6 2.5 2.4 2.3 2.2 2.1 2 1.9 1.8 1.7 1.6 1.5 1.4 Signal wavelength (um) x-cut y-cut 40 45 50 55 60 65 70 75 80 85 90 95 Theta (degrees)
OPO resonator designs STANDING-WAVE pump M1 HT pump HR signal 20 mm KTP pump PR signal HR pump signal 450 mj, 10 Hz 41% conversion Limits: M1 damage Pump feedback RING pump signal TIR prism 240 mj, 30 Hz 34% conversion No feedback No damage at full power 4, 10-mm KTP (with KTA 330 mj, 100 Hz >30% conversion)
KTP OPO engineered for CLH
Complete OPO-based lidar system
Application of CLEAR lidar to urban areas http://www.ioe.ucla.edu/clear/default.htm
Tandem OPO for infrared DIAL
Tandem OPO scheme Angle-tuned Pump-tuned, NCPM 1.5-3.6 μm Nd-doped, Q-switched laser KTA OPO CdSe OPO 3.3-11 μm Nd-doped seed laser IR seed source IR seed source Or: PPLN, other KTP isomorphs Or: AgGaSe 2 ZnGeP 2
Tandem OPO tuning with x- and y-cut KTA 12 11 10 9 Wavelength (um) 8 7 6 5 CdSe signal and idler y-cut KTA x-cut KTA 4 3 2 KTA signal and idler 1 45 50 55 60 65 70 75 80 85 90 KTA Phasematch angle (degrees)
Seeded Nd:YLF ring pump laser HR Pockels cell λ/2 Locking Electronics 60 mj @ 1053 nm Aperture OC HR PD Nd:YLF rod Polarizer Dove prism PZT HR Seed laser Optical isolator
Tandem OPO demonstration CdSe OPO signal CdSe OPO idler 8.3-10.6 um 3-4.5 mj KTA OPO idler 3.0-3.45 um CdSe EOSI 2010 External Cavity Diode Laser 1530-1560 nm Seed laser KTA OPO idler >200 mj, 20 Hz Nd:YLF pump laser Optical isolator KTA 40-50 mj signal 25 mj idler
Other remote-sensing efforts Amplified, diode-pumped, short-pulse lasers for precision altimetry (NASA Goddard) < 1 ns, 0.2 mj, 2 khz, 532 nm (SLR2000) < 10 ns, 10 mj, 1 khz, 1064 nm (satellite?) High-energy Nd:YLF lasers for space (NASA Langley) Conduction-cooled, diode-pumped, 23% slope efficiency Diode-pumped rod, 110 mj/pulse, double-pulse, 10 Hz High-power, single-frequency UV (349 nm) sources for edge-filter wind sensing (NASA Goddard) Efficient design, khz pulse rate Aircraft based Scalable to space-based
Conclusions Advances in solid state laser and nonlinear optical materials have allowed development of new sources for active remote sensing Tunable Ti:sapphire lasers with nonlinear conversion generate tunable UV for a variety of species detection, including ozone Large-aperture KTP and KTA crystals can shift the output of Nddoped lasers into the eyesafe wavelength region, for groundbased aerosol sensing in populated areas Tandem OPO systems provide broad infrared wavelength coverage, to detect a number of molecules with DIAL systems Diode-pumped lasers are now being developed to operate with higher efficiency and better reliability, suited for space-based sensors
Lamp-pumped, Nd oscillator-amplifier Prism Pump cavity Nd:YAG or YLF rods Output at 1064 nm (YAG) 1053 nm (YLF) Flashlamp Output mirror HR mirror EO Q-switch Prism Risley wedges Risley wedge Waveplate Polarizer
Ti:sapphire based ozone lidar transmitter schematic Pump Laser Nd:YLF Oscillator Isolator Nd:YLF Amplifier SHG SHG Beam Dump Beam Dump Telescope HR on scanner Output coupler (GRM) Telescope Faraday Rotator Ti:Sapphire Laser Ti:Sapphire crystals λ/2 Seed Laser Module Isolator 925 nm Isolator 945 nm λ/2 LBO SHG BBO CW Seed Diode Laser #1 925 nm, 20 mw Reshaping Optics BBO LBO THG CW Seed Diode Laser #2 945 nm, 20 mw Reshaping Optics Beam Dump
Angle-tuning data on KTA OPO 3.8 3.6 3.4 3.2 Wavelength (um) 3.0 2.8 2.6 2.4 2.2 2.0 y-cut idler data x-cut idler data x-cut signal data y-cut signal data 1.8 1.6 1.4 1.2 45 50 55 60 65 70 75 80 85 90 Angle (degrees)
I/O data for x- and y-cut KTA 60 OPO output energy (mj) 50 40 30 20 y-cut NCPM signal y-cut NCPM idler x-cut 66 deg. signal x-cut 66 deg. idler 10 0 0 50 100 150 200 250 Pump energy (mj)
CdSe OPO I/O data 5 4.5 Total OPO energy (mj) 4 3.5 3 2.5 2 1.5 3.45 um pump 3.18 um pump 1 0.5 0 0 5 10 15 20 25 30 Pump energy (mj)
CdSe OPO pump and signal pulse profiles
Composite actual tuning curve for Tandem OPO Wavelength ( m) 12 11 10 9 8 7 6 5 4 3 2 1 x-cut KTA CdSe idler CdSe signal KTA idler KTA signal 45 50 55 60 65 70 75 80 85 90 Angle (degrees)