Transcript Advances in mid and far infrared coherent sources and

Advances in mid and far infrared
coherent sources and their
applications
Valdas Pasiskevicius
Applied Physics, KTH
Outline
• Spectral ranges
• Application areas
• Radiation sources:
coherent vs incoherent
• MIR, FIR coherent sources:
technology options
• Developments at KTH
• Beyond state of the art
Spectral ranges
MIR: = 2 µm – 30 µm (150 THz – 10 THz)
Cr2+, Fe3+
Spectral ranges
FIR: = 300 µm – 30 µm (0.1 THz – 10 THz)
FEL
NLO
QCL
HCN
HCOOH
C2H5OH
CH3OH
D 2O
30
130
230
330
Wavelength, µm
430
530
Options: coherent vs incoherent
6
10
NLO
NLO
4
P, W/cm
-1
10
Er:ZBLAN
2
10
QCL LD
0
10
10
-2
10
-4
10
-6
-1
TBB=2000 K, =1cm , A=10 mm
0
20
40
, m
60
80
2
100
Advantages of coherent sources:
• High power
• High spectral power density
• High brightness
• High wall-plug efficiency
Advantages of incoherent sources:
• Broad range
• Inexpensive
Benefiting Applications:
• All except simple spectroscopy
Main application:
• Spectroscopy
[G. P. Williams, Rev. Sci.Instr. 73, 1461 (2002)]
Applications: Sensing
• Strong transitions at fundamental frequencies
• Molecular fingerprints
• MIR – ro-vibrational transitions (all material states)
• FIR – rotational transitions (gasses, liquids)
• FIR – collective vibrational modes (solids)
Sensing (monitoring) requirements:
• Several fixed (tunable) wavelengths
• Narrow linewidth: ~GHz or less
• High power and high brightness for DIAL and countermeasures
Applications: Proteomics
• Label-free
• Site specific information
• Time resolved protein reactions
Spores of B. thuringiensis ssp. kurstaki and B. subtilis
49760
[C. Kötting et al Proc.Nat.Acad.Sci. 103, 13911 (2006)]
[T.J.Johnson et al Chem.Phys.Lett. 403, 152 (2005)]
Applications:Imaging, Inspection
Fuel tank of Schuttle launch rocket behind foam
• Dielectric solids: no rotational DoFs
• Transparent in FIR
• Low scattering losses
THz stress-induced birefringence imaging
Carbon-fiber composite helicopter stator
[Picometrix, Inc.]
[M.Koch, OPN, 18,21 (2007)]
Applications: Fuel industry
[M.A. Aliske et al Fuel, 86, 1461 (2007)]
Applications:Surgical
MIR lasers:
• High H2O absorption
• Less tissue-specific
• Smaller heated volume
• Lower collateral damage
Applications:Surgical
Defficiencies of current procedures
Laser induced shock-wave effect on water
Er:YAG 100 ns, 50 MW/cm2
[A.Vogel et al Chem.Rev. 103, 577 (2003)]
Shock-wave damage
Applications: Detection of explosives
Applications: XUV and as pulse generation
Atom in high optical field:
Tunnel ionization , classical axceleration in electric field
XUV photon cutoff energy:  XUV  I p  3.17U p ~ I p  3.17
Ionization potential + Ponderomotive energy
E
2

2
0
[M. Levenstein et al, PRA, 49, 2117 (1994)]
High intensity (ultrashort) in MIR are advantageous
Applications: XUV and as pulse generation
[R. Kienbergeret al Nature, 427, 817 (2004)]
• CEP phase-stabilized pulses required
• Currently all-passive CEP stabilization by (2):(2) or (3) NLO processes
State of the art: QCL
1THz ~ 4.1 meV ~ 47.6 K
hphonon ~ 30meV
Main breakthroughs:
• Resonant optical-phonon depopulation
• Metal-metal waveguides
[B. S. Williams, Nature Photonics, 1, 517 (2007) ]
State of the art: Solid state lasers
Engineering toolbox:
• Crystal field – Tailorable transition energies
• Structural disorder - inhomogeneous broadening – Gain spectral width (fs)
• Phonon Spectrum – thermal conductivity, nonratiative lifetime
• Growth technologies – size, cost
• Coating technologies – damage threshold
• Laser diode technology – reliability, power, new materials (1.9µm InGaAsSb/GaSb)
MIR high power (W-kW) laser options:
CO2 – 10µm
CO - 5µm
Er3+ - 3µm
Cr2+ – 2.2 -2.8 µm
Ho3+ - 2.1 µm
Tm3+ - 1.85µm – 2.1 µm
Beyond state of the art: New SSL materials
Main search strategy:
• Low phonon energy materials
• Enhanced transparency in MIR
Generic formula: Re3+:MePb2Hal5
Re=Pr, Nd, Er, Tb, Dy, Ho
Me=K,Rb
Hal=Cl, Br
Transparency regions:
KPb2Cl5 0.4 µm – 20 µm
KPb2Br5 0.4 µm – 30 µm
RbPb2Br5 0.37 µm – 30 µm
Nonlinear optical sources
Characteristics:
• Tunable – depends on nonlinear material
• No quantum defect – High peak and average power
• From CW to fs
• High efficiency
DFG
OPA
i   p  s
OPO
 p  s  i
Nonlinear optical materials for MIR, FIR
Required and Desirable properties:
• High transmission at pump wavelength around 1µm
• Absence of two-photon absorption at pump wavelength
• High transmission in MIR
• High nonlinearity
• High optical damage threshold
• Engineerability (QPM structuring or composition variation)
• Non-hygroscopic
• Feasibility of large-volume crystal growth
Main classes of MIR, FIR NLO materials:
• Oxides: KTiOPO4 (KTP), RbTiOPO4 (RTP), LiNbO3, LiTaO3...
Engineerable, can be pumped in NIR
MIR Transmission limited to ~4 µm, 80µm - 300µm
• Semiconductors: GaAs, GaP, ZnGeP2 (ZGP), AgGa1−x InxS2, ...
MIR tranmission to 20 µm, FIR 60µm – 300 µm
Absorbing at 1 µm
• Organic: 4-N,N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST)
Very high nonlinearity 30xKTP, good MIR, FIR transmission
Very difficult to grow, Hygroscopic
Engineerable nonlinear optical materials
OP-GaAs (Stanford)
PP-KTP (KTH) period 800 nm, over 5 mm
[L.A.Eyres et al APL, 79, 904 (2001)]
[C. Canalias et al Nature Photonics,1, 459 (2001)]
State of the art: OPOs
High-energy ns tunable OPO
PP-RbTiOPO4
Signal / Idler wavelength (m)
3.4
35.4 m
3.2
36.0 m
3.0
36.4 m
2.8
2.6
37.4 m
2.4
38.2 m
2.2
37.8 m
2.0
1.8
1.6
20
40
60
80
100
120
140
160
180
Temperature (°C)
[A.Fragemann, Optics Lett., 83, 3092 (2003)]
State of the art: OPOs
Cascaded PPKTP – ZGP OPO for active countermeasures
[M.Henriksson, Appl. Phys.B, 88, 37 (2007)]
Beyond state of the art: OPO
Surgical ns OPO at 6.45 µm and 6.1 µm
Target: Peak power 0.5 MW, average power 1W
State of the art: OPAs
Optical parametric amplifiers for ultrashort pulses
OP-GaAs (Stanford)
PP-KTP OPA (KTH)
Power, log scale
0
-10
p=827nm, =28µm
-20
-30
1000
2000
3000
4000
Wavelength , nm
[M.Tiihonen, etal, Appl. Phys. B, 85, 73 (2006)]
FWHM  115 THz (~1 octave)
1.08 µm - 3.8 µm
[P.S.Kuo, etal, Optics Lett., 31, 71 (2006)]
Beyond state of the art: Near-field MIR-FIR
• MIR, FIR polariton optics in ferroelectrics
• Tailoring polaritonic FIR waves with photonic crystals
• Functionalized surfaces
• Sub-wavelength sensing
[K. A. Nelson etal Nature Materials, 1, 95 (2002)]
[J. Faist, etal Optics Express, 15, 4499 (2007)]