Diapolaser

SOLID-STATE LASERS: 

Jean-Paul Pocholle SOLID-STATE LASERS

LASER COMPONENTS: 

LASER COMPONENTS Gain medium Laser emission Energy source Pumping process Light Electrical Chemical Optical resonator Cavity Solids Liquids Gases Plasmas Electron beam Doped insulators Semiconductors Laser Lamp Flash ...

PROGRESSES ON DIODE LASERS: 

PROGRESSES ON DIODE LASERS Higher performances for lower costs CW : 60 W/bar, multi kW stacks (<2 mm pitch), 10 000 hour lifetime, 35 $/W (100 $/W in 1997). QCW : 100 W/bar, 4% to 50% duty cycle, multi Joules stacks (0.1 to 2 mm pitch), 109 shot lifetime, 7 $/W. Fibre-coupled CW arrays two time cheaper than in 1996 : 4500 $ ( 20 W / 600 µm / NA 0.2). and Considerable amount of work done to make manageable light sources ! Output power and cost

SOLID-STATE LASERS : TRADITIONAL LIMITATIONS: 

SOLID-STATE LASERS : TRADITIONAL LIMITATIONS OVER PAST DECADE, R&D HAVE LED TO ENHANCED CAPABILITIES . DIODE PUMPING . HIGH EFFICIENCY ~10% . REDUCED HEAT LOAD ~1/3 THAT OF LAMP PUMPING . LONG OPERATING LIFETIME : 10 BILLION PULSES . ZIG-ZAG SLAB LASERS . HIGH POWERS (100W TO 3kW / projected 10kW) . NEARLY DIFFRACTION-LIMITED BEAM QUALITY . PHASE CONJUGATION . HIGH POWERS (100W TO 1kW) & ENERGY SCALING . DIFFRACTION-LIMITED BEAM QUALITY . SUPERIOR POINTING STABILITY . POOR EFFICIENCY : ~1% OR LESS . POOR BEAM QUALITY : ~10 to 50 XDL ."TOLERABLE" MAINTENANCE (LAMP CHANGES)

Nd:YAG ABSORPTION BANDS: 

Nd:YAG ABSORPTION BANDS Nd:YAG transmission (thickness : 2mm) Wavelength (nm) Laser diode spectrum matched with strong Nd3+ ion absorption peak

DIODE-PUMPED SOLID-STATE LASERS: 

DIODE-PUMPED SOLID-STATE LASERS . Near resonance pumping Low heat loading Reduced thermal focussing Reduced induces stress birefringence Better beam quality High beam pointing stability High pulse-to-pulse stability Reduced acoustic noise Passive or thermo-electric cooling . Smaller Size Compact Greatly lowered utility requirements : Low weight . efficient use of work area . desirable for : military, space, industrial applications and medicine . Longer Life / Long-lived Low maintenance cost : Greater reliability pump source . premium for use in space Low-voltage drive Significant advantages over conventional lamp-pumped Lasers Implications for applications

SOLID-STATE LASER vs LASER DIODES: 

SOLID-STATE LASER vs LASER DIODES Rare Earth (RE) doped crystal used as Solid-State Laser : - Energy storage system . Fluorescence lifetime of excited level : 0.1 to 10ms - Spatial mode converter . Transverse multimode pump beam transformed into TEM00 mode End-pumping Transverse pumping

FROM THE LAB. to TL PRODUCT LINE: 

FROM THE LAB. to TL PRODUCT LINE TL Product line OPUS Applications : Pump source for fs Ti:Al2O3 laser Medicine 3.5W CW @ 0.532µm

DIODE-PUMPED MOPA* LASER: 

DIODE-PUMPED MOPA* LASER * MOPA : Master Oscillator Power Amplifier Oscillator / Amplifiers Longitudinally end-pumped

Slide10: 

In 1998 : Commercial DPSSL DIVA @ TL FROM RESEARCH TO PRODUCT Energy > 50 mJ IR to 10 mJ UV Compact and air-cooled

LASER BEAM CONTROL: 

LASER BEAM CONTROL General objectives : . Correction of the spatial and temporal aberrations of the laser sources to operate close to the diffraction limit in the space and time domain . Reduce the beam divergence  Increase of the Brightness of the laser . Reduce the duration of ultrashort pulses  Increase of the peak power of the laser The Technologies : - Generation of a phase conjugate wave with a nonlinear mirror. - Generation of a correcting wavefront with a Programmable Liquid Crystal Spatial Light Modulator.

THERMALLY INDUCED OPTICAL LENS: 

THERMALLY INDUCED OPTICAL LENS Efficient diode pumping of laser crystal induces a significant thermal lensing effect and spatial distorsions of the wavefront. Thermal lensing effect of a transversally diode pumped laser medium

Slide13: 

LYRA : CW Operation @ 1064 nm Multimode operation P = 100 W M2 = 8 Single mode operation (spatial filtering) P = 21 W M2 = 1.6

PHASE CONJUGATION: 

PHASE CONJUGATION A non linear mirror generates a phase conjugate replica of the incident distorted wavefront : After a double pass through the gain media the aberrations are compensated. Wavefront correction after wavefront reflection by a non linear mirror

EXPERIMENTAL RESULTS: 

EXPERIMENTAL RESULTS (a) Spatial profiles of the beam without phase conjugation :Distorsions due to wavefront aberrations (b) Diffraction limited beam obtained from the self adaptative Nd:YAG phase conjugate oscillator. Typical performances 160mJ / 30Hz / 15ns single mode

INTRACAVITY PHASE PLATE for MODE CONTROL and ABERRATION CORRECTIONS: 

INTRACAVITY PHASE PLATE for MODE CONTROL and ABERRATION CORRECTIONS Objective : An holographic phase plate (HPP) can control the output beam profile of the laser cavity The phase plate is realized by holographic recording of the proper wavefront with a high efficiency photopolymer material

EXPERIMENTAL RESULTS: 

EXPERIMENTAL RESULTS . With the holographic plate (HPP), the laser emits a top hat intensity distribution. . In principle any Intensity and Phase distribution can be obtained. Gaussian beam Better extraction efficiency « Top-hat » beam profile Without the HPP With the HPP

NEW CONCEPTS FOR LASER BEAM STEERING: 

NEW CONCEPTS FOR LASER BEAM STEERING Objective : - Fast and non mechanical beam deflection - Multi beam generation from a single source Technologies : - Acousto-optic deflectors - Phased array optical antennas - Intracavity mode selection Applications in Optronics - Multi-target tracking and designation - Counter measurements - Active imaging

LASER OSCILLATOR WITH INTRACAVITY BEAM STEERING: 

LASER OSCILLATOR WITH INTRACAVITY BEAM STEERING A L. C. SLM selects one or several directions of the oscillating modes. The compact amplifier exhibits a large angular acceptance  30°.

INTRACAVITY BEAM DEFLECTION: 

INTRACAVITY BEAM DEFLECTION (a) Selection of one direction (b) Simultaneous generation with the SLM of several beams Experimental Results

GENERATION of a CORRECTING WAVEFRONT with a PROGRAMMABLE LIQUID CRYSTAL SLM: 

GENERATION of a CORRECTING WAVEFRONT with a PROGRAMMABLE LIQUID CRYSTAL SLM A LC SLM can control the spatial distribution of the phase of a wavefront. The SLM is optically adressed by the projection of the image of a L.C. TV on the photoconductor of the device. Operating principle of the LC-SLM

OPERATING PRINCIPLE of an ADAPTIVE PHASE CORRECTION of a LASER BEAM: 

OPERATING PRINCIPLE of an ADAPTIVE PHASE CORRECTION of a LASER BEAM The wavefront aberrations are measured and a feedback loop adresses the progammable LC phase plate- wavefronts correction of the laser beam @ l =1.06µm is achieved after few iterations.

EXPERIMENTAL RESULTS OF THE ADAPTIVE LC PHASE CORRECTION: 

EXPERIMENTAL RESULTS OF THE ADAPTIVE LC PHASE CORRECTION (a) The focal spot is degraded by the aberrations. (b) The spot quality close to diffraction is recovered after correction by the LC phase SLM. (c) Phase correction after integration of the module in a 100TW (1014W) laser chain @ LULI-Ecole Polytechnique. Observation of the beam at the focus of a lens.

CONTROLLING THE DURATION of ULTRASHORT fs LASER PULSES: 

CONTROLLING THE DURATION of ULTRASHORT fs LASER PULSES The Ti-Saphire laser medium exhibits an extremely large gain bandwidth > 200nm around l = 800nm : It can deliver ultrashort fs pulses.  Order of magnitude : A 10fs pulse = 3µm length in the air Examples of relations between the pulse duration and spectral bandwith

CHIRPED PULSE AMPLIFICATION (CPA) LASER ARCHITECTURE: 

CHIRPED PULSE AMPLIFICATION (CPA) LASER ARCHITECTURE For obtaining extremely high peak powers with fs (10-15 s) pulse duration a new laser architecture was designed. CPA LASER chain. Pulse stretching and compression are realized by grating devices Like in Radars, it requires pulse stretching, pulse amplification, pulse compression.

THE PROBLEM of the PULSE DISPERSION CORRECTION in the LASER CHAIN: 

THE PROBLEM of the PULSE DISPERSION CORRECTION in the LASER CHAIN Optical materials of the laser chain are dispersive To recover the initial pulse width delivered by the fs oscillator, new fixed or programmable optical components must be introduced  They introduce a group delay dispersion which stretches the pulse

A CHIRPED MIRROR WITH A CONTROLED DISPERSION LAW: 

A CHIRPED MIRROR WITH A CONTROLED DISPERSION LAW The required dispersion law is realized by a stack of multidielectric layers for a given spectral bandwidth. . It can compensate for the pulse dispersion in a fs Ti:Saphire oscillator Schematic of the chirped mirror

PROGRAMMABLE ACOUSTO-OPTIC COMPONENT for fs PULSE DISPERSION COMPENSATION / or PULSE SHAPING: 

PROGRAMMABLE ACOUSTO-OPTIC COMPONENT for fs PULSE DISPERSION COMPENSATION / or PULSE SHAPING A colinear acousto-optic filter permits the control of the dispersion of the ultra- short pulse : Each spectral component of the pulse are diffracted at different position by the AO interaction. Operating principle of the AO programmable filter Example of a pulse shaping function : Three pulses are generated by proper driving of the AO filter

Slide29: 

WHAT‘s NEW ? Over the last years, tremendous improvements were achieved : on diode : power, brightness, efficiency, cost, utilisation on material : thermal management, fracture threshold 100W to multi-kW lasers 1 to 10 time diffraction limited FANUC Ltd Japan.

OPTRONICS: 

OPTRONICS ADVANCED RESEARCH on NON LINEAR OPTICS

OPO : OPTICAL PARAMETRIC OSCILLATOR: 

OPO : OPTICAL PARAMETRIC OSCILLATOR Tunable laser source : IR Bands II & III

PARAMETRIC INTERACTION: 

PARAMETRIC INTERACTION NL Crystal  Pump Signal Idler input Mirror Output Mirror Energy Conservation (Frequency matching) Momentum Conservation (wavevector matching) Pump Optical Parametric Oscillator (OPO)

ANGLE TUNING CURVES FOR LiNbO3 OPO: 

ANGLE TUNING CURVES FOR LiNbO3 OPO Signal Idler

IR TUNABLE SOURCES BASED ON SOLID-STATE NONLINEAR DEVICES: 

IR TUNABLE SOURCES BASED ON SOLID-STATE NONLINEAR DEVICES 1) TWO CASCADED OPOs Nd:YAG Laser @ 1.064µm p s1 i1 s2 i2 LiNbO3 / KTP OPO AgGaSe2 OPO Nd:YAG Laser @ 1.064µm p s1 i1 IR LiNbO3 / KTP OPO DFG AgGaSe2 TWO ALTERNATIVES SCHEMES : 2) COUPLED OPO + DFG (Difference Frequency Generation)

ADVANCED NONLINEAR MATERIALS: 

ADVANCED NONLINEAR MATERIALS Quasi-Phase-Matched (QPM) materials have periodically modulated non-linear properties to reset the phase mismatch between interacting waves. d They are attractive for frequency conversion of Nd:YAG lasers to the infrared for OCM applications, because of : efficiency non-critical interactions multi-wavelength conversion

QPM MATERIALS: LiNbO3 (PPLN) for l = 1 to 5 µm: 

QPM MATERIALS: LiNbO3 (PPLN) for l = 1 to 5 µm The modulation is obtained through the bulk material (1 mm) using periodic electric field poling (20 kV/mm). Nd:YAG pumped PPLN OPO emitting near 1.5 (signal) and 4 µm (idler) Periodic poling set-up

QPM MATERIALS : GaAs for l > 5 µm: 

QPM MATERIALS : GaAs for l > 5 µm The modulation is obtained by diffusion-bonding thin wafers of GaAs with alternated orientations (typically 1 cm long / 100 wafers). IR transmission of a 1 cm long sample Second harmonic generation of a CO2 laser 5 mm sample

ALL SOLID-STATE TUNABLE LASER SOURCES: 

ALL SOLID-STATE TUNABLE LASER SOURCES DIODE PUMPING TECHNOLOGIES AND NONLINEAR OPTICAL SOLID-STATE MODULES ALLOW THE DEVELOPMENT OF : EFFICIENT & COMPACT SOLID-STATE LASER SOURCES OPERATION in DIVERSE BROAD SPECTRAL RANGES (UV, VISIBLE, EYESAFE Source, IR) FOR SCIENTIFIC AND CIVILIAN APPLICATIONS : . Laser Radar, LIDAR, Pollutant detection and monitoring … FOR DEFENCE : . Countermeasures, Identification, Remote sensing ...

SOME LASER APPLICATIONS: 

SOME LASER APPLICATIONS Defence : . Designator . Illumination or gated viewing . Rangefinder profiler . Laser Radar . EO Countermeasures . Lidar . Obstacle avoidance Chemical/Biological agent detection . Beamriders . Imaging Seekers . Laser Jammers Industrial field : . Perforating / Drilling . Engraving . Cutting / Profiling . Rapid Prototyping . Welding . Marking / Coding . Paint Removal . Scribing