High power and single frequency quantum. cascade lasers for gas sensing. Stéphane Blaser

Transcription

1 High power and single frequency quantum cascade lasers for gas sensing Stéphane Blaser Alpes Lasers: Yargo Bonetti Lubos Hvozdara Antoine Muller University of Neuchâtel: Marcella Giovannini Nicolas Hoyler Mattias Beck Jérome Faist

2 Outline Introduction Applications High power Fabry-Pérot devices High power pulsed DFB devices Cryogenic continuous-wave devices Reliability of the devices

3 Interband vs intersubband E E f E 12 k Interband transition - bipolar - photon energy limited by bandgap E g of material - Telecom, CD, DVD, E E 12 E f k Intersubband transition - unipolar, narrow gain - photon energy depends on layer thickness and can be tailored

4 Quantum cascade lasers Cascade -eache-emits N photons Active region / injector - active region population inversion which must be engineered -injector avoid fields domains and cools down the electrons τ32 > τ 21 T e >>T l τ 32 τ 21 T e ~T l active region relaxation / injection MBE - growth of thin layers - sharp interfaces

5 InP CW pulsed State of the art: QCL performances Atmospheric windows GaAs Peltier Temperature [K] Reststrahlen band LN Wavelength [µm] CW pulsed - Good Mid-IR coverage - Terahertz promising Data: Uni Neuchâtel Alpes Lasers Bell Labs Thales TU Vienna Northwestern Uni W. Schottky

6 Spectrum covered by Alpes Lasers dfb QCLs infrared UV 1 cm 1 cm 1 mm 1 µm 1 µm.8 µm.4 µm radio RADAR QCL Wavelength [µm] CCl2 O 2 NH3 F4 Si O3 N2 O CH4 C2 H 4 C5 H 1 O CCl2 O CO N2 O CO2 C2 H 4 O NH maser 3.1 THz p-ge laser 1 THz CO 2 laser High power QC lasers using new designs: Bound-to-continuum (patent n wo 2/19485A1) Two-phonon resonance (patent n wo 2/23686A1) Wavenumber [cm -1 ]

7 Applications: chemical sensing by optical spectroscopy Vibrational mode of molecules in Mid-IR Detection techniques: photo-acoustic TILDAS cavity ringdown Can be used for trace gas analysis, process control liquid detection spectroscopy Needs: high-power laser narrow linewidth (single mode) continuous-wave operation Talks in TDLS 3: Barry McManus: Trace Gas Instrumentation Using Pulsed Quantum Cascade Lasers Mark Zahniser: Trace Gas Measurements Using Pulsed Quantum Cascade Lasers Frank Tittel: Chemical Sensing with Quantum Cascade Lasers

8 Applications: chemical sensing by optical spectroscopy Typical applications: atmosphere diagnostics pollution monitoring non-invasive medical diagnostics detection of biological contaminants, drugs or explosives ammonia (NH 3 ) monitoring in process industry CO, NO, SO 2, SO 3 (e.g. in combustion processes) CH 4, HF, H 2 S, in petro-chemical processing facilities (e.g. gas leak detector) CO 2, O 3 for environment monitoring Large organic hydrocarbon molecules like benzene

9 Other applications Telecommunications Free-space optical data transmission for the last mile (high speed with no need for licence and better operation in fog, compared to λ = 1.55 µm) Terahertz field Astronomy Medical imaging Chemical detection Telecommunications for local area network (LAN) Talks yesterday: Ruedeger Koehler: Terahertz Quantum Cascade Lasers Daniel Hofstetter: Latest Progress on Intersubband Devices: Lasers and Detectors from the Near- to the Far-Infrared

10 High average power FP QCL: RT-HP-FP-15-X K, 6% 3K, 2% Voltage [V] Average power [W] Current [A].2.1 Characteristics Back-facet coated λ = 7.9 Average power: P = 15 mw threshold current density: j th = 3. ka/cm : P =.82 W (6% dc) j th =.75 ka/cm 2 P in CW: P = 3mW (j th =.78 ka/cm 2 )

11 Continuous-wave FP QCL on Peltier C -2 C -3 C Voltage [V] Average power [mw] CW Current [A] 1 Characteristics 1.5 mm-long, 12 µm-wide laser Buried-heterostructure Back-facet coating CW operation at λ 9.2 µm on C: Average power: P = 42 mw Threshold current density: j th = 3.8 ka/cm 2 typically designed for Free Space Optics data transmission

12 High average power DFB QCL: RT-HP-DFB-2-X Distributed feedback QC laser at 8.35µm with InP top cladding 1 35 Characteristics mm-long, 28µm-wide laser λ 8.35 C: Average power (2% dc): P = 32 mw (1.6 W peak power) threshold current density: j th = 2.9 ka/cm 2 Voltage C : P = 25 mw (1.25W peak power) j th = 3.8 ka/cm 2 Average power [mw] -3 C C 3 C Current [A]

13 High average power DFB QCL: RT-HP-DFB-2-X Current [A] Voltage [V] Average power [mw] -3 C C 3 C C, 14V 3 C, 12V 15 C, 14V 15 C, 12V C, 14V C, 12V C 3 C Characteristics λ 8.35 µm Single-mode operation at T C with SMSR 4 db (At high bias, single-mode operation with SMSR 2 db) 4 db Wavelength [µm]

14 Long-wavelength (λ 16.4µm) B2C DFB QCL: RT-P-DFB-1-X Laser based on a bound to continuum design, λ 16.4 µm Rochat et al., APL 79, 4271 (21) Current [A] DC voltage fed to LDD [V] Average power [mw] -3 C -15 C C 15 C 3 C 4 C 5 C Characteristics 3 mm-long, 44µm-wide laser λ 16.4 C: Average power (1.5% dc): P = 1.5 mw (1 mw peak power) Threshold current density: j th = 5.4 ka/cm C : P =.5 mw (33 mw peak power) j th = 7.9 ka/cm 2

15 Long-wavelength (λ 16.4µm) B2C DFB QCL: RT-P-DFB-1-X C, 21V -3 C, 27V -15 C, 21V -15 C, 27V C, 23V C, 28V 15 C, 24V 15 C, 29V 3 C, 26V 3 C, 3V 4 C, 27V 4 C, 32V 5 C, 28V 5 C, 32V Characteristics 3mm-long, 44µm-wide laser λ 16.4 µm single-mode emission: Side Mode Suppression Ratio > 25 db tuning range: cm -1 (16.51 µm) at 5 C to 61.3 cm -1 (16.38 µm) at -3 C Normalized intensity Wavenumbers [cm-1]

16 CW operation at λ 6.73µm: LN2-CW-DFB-1-X 1.2 Characteristics K 13K 12K 1K 8K mm-long, 23 µm-wide laser CW operation at λ 6.73 K: Average power P =.2 W Threshold current density: j th = 1. ka/cm 2 Voltage [V] Average power [W] Current [A]

17 CW operation at λ 6.73µm: LN2-CW-DFB-1-X K, 5mA 1K, 7mA 1K, 65mA 1K, 55mA 1K, 45mA 8K, 75mA 8K, 7mA 8K, 6mA 8K, 5mA 8K, 4mA Wavelength [µm] Characteristics 1.5 mm-long, 23 µm-wide laser CW operation at λ 6.73 µm single-mode emission: Side Mode Suppression Ratio > 3 db tuning range: cm -1 (6.744 µm) at 12K to cm -1 (6.722 µm) at 8K Normalized intensity Wavenumbers [cm -1 ]

18 Terahertz QC laser THz QC laser based on a bound to continuum design, λ 87 µm Structure grown at University of Neuchâtel (L. Ajili, G. Scalari, M. Beck and M. Giovannini) j [A/cm 2 ] Duty cycle 2.5% Jth=267 A/cm 2 1k 5k 7k 78k Characteristics THz QC laser: λ 87 µm 2.7mm-long, 2µm-wide laser back-facet K: Peak power (2.5% dc): P = 14 mw threshold current density: j th = 267 A/cm 2 Voltage [V] Peak power [mw] Emission energy [mev] Current[A] pulsed operation up to 78K CW operation up to 3 K

19 Reliability of the devices Lifetime measurement (partly with HR coating) ageing at 13 C and 2 % duty-cycle, monitor signal at 3 C (HR) c1 (HR) c11 (HR) c13 c14 c15 Normalized output power Time [hours] => lifetime of the devices > 4 years

20 Tuning Advantages of QCLs DFB Pulsed (CW) CW Pulsed FP CW Pulsed CW RT LN2 RT LN2 3 mw (4mW) mw 2 mw.8 W 2 mw < 33 MHz < 3.5 MHz 1-4 % 1-4 %.4 %.4 % N/A N/A Portable Linewidth Temp. cycling Power Temperature Type Duty-cycle