Boston Electronics Corporation 91 Boylston Street, Brookline, Massachusetts 02445 USA (800)347-5445 or (617)566-3821 fax (617)731-0935 www.boselec.com boselec@boselec.com Room Temperature TUNABLE IR DIODE LASERS from Alpes Lasers Readily available: Single Mode many devices between 4.3 and 10.4 µm Multimode 5.0 to 6.2 and 8.5 to 10.6 µm Built to order: 3.
3.5 3 2.5 2 1.5 1 0.5 Alpes #sb9 at different temps with different drive voltages -30C nm 0C 4/8/2004 +30C Boston Electronics (800)347-5445 or qcl@boselec.
High power and single frequency quantum cascade lasers for chemical sensing Stéphane Blaser final version: http://www.alpeslasers.ch/Conference-papers/QCLworkshop03.pdf Page 1 of 51 Boston Electronics * QCL@boselec.com Collaborators Yargo Bonetti Lubos Hvozdara Antoine Muller Guillaume Vandeputte Hege Andersen This work was done in collaboration with the University of Neuchâtel Page 2 of 51 Marcella Giovannini Nicolas Hoyler Mattias Beck Jérome Faist Boston Electronics * QCL@boselec.
Outline • Company profile • Introduction - state of the art – High power Fabry-Pérot devices • Applications • Distributed-feedback lasers – High power pulsed DFB devices – >77K operating continuous-wave DFB devices • Reliability • Production Page 3 of 51 Boston Electronics * QCL@boselec.
Company profile • > 30 man-years experience • 7 patents on QCL technologies • > 150 devices sold • > 50 customers • turnover 2003: > 1.3 MCHF • average growth rate: 100% / year Page 5 of 51 Boston Electronics * QCL@boselec.com Quantum cascade lasers Page 6 of 51 Boston Electronics * QCL@boselec.
Interband vs intersubband E E Ef Ef E12 E12 k|| k|| • Interband transition - bipolar - photon energy limited by bandgap Eg of material - Telecom, CD, DVD,… • Intersubband transition - unipolar, narrow gain - photon energy depends on layer thickness and can be tailored Page 7 of 51 Boston Electronics * QCL@boselec.
State of the art: QCL performances Atmospheric windows Reststrahlen band Temperature [K] 150 Peltier LN2 0 2 5 10 20 50 100 CW pulsed 678 300 CW pulsed 678 450 InP GaAs - Good Mid-IR coverage - Terahertz promising Data: MIR FIR Uni Neuchâtel NEST Pisa Alpes Lasers MIT Bell Labs Uni Neuchâtel Thales TU Vienna Northwestern Uni W. Schottky/TU Munich Wavelength [µm] Page 9 of 51 Boston Electronics * QCL@boselec.
Two-phonon structure at 8 Pm injection barrier arrow QW/barrier pair Based on two-phonon resonances design extraction barrier InGaAs/InAlAs-based heterostructure with 'Ec = 0.52eV Grown by MBE on InP substrate 35 periods n-d ope d 4Q Wa ctiv e reg i on one per iod 41, 16, 8, 53, 10, 52, 11, 45, 21, 29, 15, 28, 16, 28, 17, 27, 18, 25, 21, 25, 26, 24, 29, 24 Page 11 of 51 Boston Electronics * QCL@boselec.com RT-HP-FP-150-1266 16 0.9 14 0.8 96K, 60% 300K, 20% 12 0.7 0.6 10 2.
Array of lasers DUAL-RT-HP-FP-40-1266 50 0 1 2 er dn 5 arr ay of 2 30 20 las ru p 10 3 4 Current [A] 10 5 6 7 0 Characteristics Average power [mW] las e 15 0 40 rs T = -25°C duty-cycle = 10% las e DC voltage fed to LDD [V] 20 both lasers: 1.5 mm-long, 28 µm-wide λ ≈ 7.9 µm T = -25°C, duty-cyle = 10% j th laser Average power I th [A] up 25.4 mW 1.8 4.29 dn 22.6 mW 1.6 3.81 array 44.9 mW 3.4 4.
Applications: telecom • Telecommunications – Free-space optical data transmission for the last mile (high speed with no need for licence and better operation in fog, compared to O = 1.55 Pm) 4 to 7 years 100 Gbps 40 Gbps 1 to 4 years Bandwidth 10 Gbps Present 1 Gbps 622 Mbps 155 Mbps 1 Mbps Local Network Last Mile Metro Backbone Long-Haul Backbone R. Martini et al., IEE Elect. Lett. 37 (11), p. 1290, 2001. S. Blaser et al., IEE Elect. Lett. 37 (12), p. 778, 2001.
Application fields • Chemical sensing or trace gas measurements – – – – – • process development environmental science forensic science process gas control liquid detection spectroscopy Medical diagnostics – breath analyzer – glucose dosage • Remote sensing – leak detection – exhaust plume measurement – combat gas detection Page 17 of 51 Boston Electronics * QCL@boselec.
0.4 µm 0.8 µm 10 µm infrared UV QCL CO2 laser 100 µm 10 THz NH3 maser RADAR 0.1 THz radio p-Ge laser 1 mm 1 cm 10 cm Spectrum covered by Alpes Lasers dfb QCLs Wavelength [µm] 10.0 7.0 5.0 4.0 3.0 500 1000 1500 2000 CO2 CO N2O CCl2O C5H10O C2H4 N2O CH4 NH3 F4Si O3 CCl2O2 C2H4O 20.0 2500 Wavenumber [cm-1] Page 19 of 51 Boston Electronics * QCL@boselec.com Single-mode operation: distributed-feedback QCLs Page 20 of 51 Boston Electronics * QCL@boselec.
How does a DFB work? gain DFB: periodic grating => waves coupling => high wavelength selectivity gain complex-coupled DFB: • lasing mode closest to the stopband • stopband § coupling strength Page 21 of 51 Amplified light bounces in the cavity Wavelength [µm] 9.1 9 8.9 8.8 stopband ∆ν = 1.19 cm-1 180 K Intensity [a.u.] Fabry-Pérot laser: 200 K 220 K 1095 1100 1105 1110 1115 1120 1125 1130 1135 1140 Frequency [cm-1] Boston Electronics * QCL@boselec.com Distributed-feedback technologies D.
High average power DFB QCL RT-HP-DFB-20-1200 Distributed feedback QC laser at 8.35Pm with InP top cladding 35 30 Voltage [V] 8 25 6 -30°C 20 0°C 15 4 30°C 10 2 0 5 0 1 2 3 4 5 6 7 Characteristics Average power [mW] 10 3mm-long, 28µm-wide laser λ ≈ 8.35 µm @-30°C: Average power (2% dc): P = 32 mW (1.6 W peak power) threshold current: Ith = 2.44 A (jth = 2.9 kA/cm2) @30°C : P = 25 mW (1.25W peak power) Ith = 3.2 A (jth = 3.
RT-P-DFB-1-608 Long-wavelength (O§16.4Pm) B2C DFB QCL Laser based on a bound to continuum design, O § 16.4 Pm Rochat et al., APL 79, 4271 (2001) 1.6 30 1.4 -30°C -15°C 0°C 15°C 30°C 40°C 50°C 25 20 1.2 1.0 0.8 15 0.6 10 0.4 5 0.2 0 0 2 4 6 8 10 12 Characteristics Average power [mW] DC voltage fed to LDD [V] 35 3 mm-long, 44µm-wide laser λ ≈ 16.4 µm @-30°C: Average power (1.5% dc): P = 1.5 mW (100 mW peak power) Threshold current: Ith = 7.1 A (jth=5.4 kA/cm2) @50°C : P = 0.
How does a DFB tune? Page 27 of 51 Boston Electronics * QCL@boselec.com How does a DFB tune? Tuning always due to thermal drift (carrier effects can be neglected!) Tact wavelength selection : λ = 2⋅ n eff ⋅ Λ grating neff =neff (T) Tsub Page 28 of 51 dλ λ = dneff neff Boston Electronics * QCL@boselec.
How does a DFB tune? Active region heating: Tact Tact = Tsub + I⋅ U ⋅ δ ⋅ R th (+I DCU DC ⋅ R th ) ∆T = Tact − Tsub Tsub If 'T = 100°C = 60°C = 30°C 100% chance of laser-destruction (thermal stress) depends of mounting / laser -> dangerous OK Different possibilities of thermal tuning: { substrate temperature additional bias current pulse length (chirping) pulse current duty-cycle Page 29 of 51 Boston Electronics * QCL@boselec.
Tuning by DC bias-induced heating by DC bias-induced heating t2 Tsub≈cst I ≈ 0.5 - 5 A t1 I by changing Tsub t1 Tsub 1 t1 Tsub 2 t2 IDC (≈ 100 - 200 mA) I ≈ 0.5 - 5 A t t Rth = L I ∆T Vdevice ⋅ IDC L t1 t2 Popt ≈ cst t2 I I 'T § 30°C => -0.2% 'Q Q @ >1kHz 'T § 60°C => -0.4% 'Q Q @ 0.01Hz Page 31 of 51 Boston Electronics * QCL@boselec.com Intensity [arb. units] Thermal chirping during pulse 1.2 300 K I = 3.14 A gate width = 3 ns peak power = 50 mW drift with time: 0.
Pulse length dependence of linewidth Linewidth [cm-1] 0.6 Aerodyne measurements (diff. device!) FTIR spectrometer grating spectrometer calculation 0.5 0.4 Need for a good compromise: • too long: limited by thermal chirping • too short: limited by the time evolution of the lasing mode 0.3 0.2 fundamental limits 0.1 0 0 20 40 60 80 Pulse length [ns] for narrower linewidth: cw operation Hofstetter et al., Opt. Lett. 26, p.887 (2001) Page 33 of 51 Boston Electronics * QCL@boselec.
CW operation at O § 6.73Pm LN2-CW-DFB-100-1485 Wavelength [µm] 6.75 Normalized intensity 1 6.74 6.73 6.72 Characteristics 120K, 500mA 100K, 650mA 100K, 550mA 100K, 450mA 80K, 600mA 80K, 500mA 80K, 400mA 0.1 1.5 mm-long, 23 µm-wide laser CW operation at λ ≈ 6.73 µm Single-mode emission: Side Mode Suppression Ratio > 30 dB (limited by the resolution of the FTIR) 0.01 Tuning range: ∆ν = 4.9 cm-1 at 1485 cm-1 (0.33%) (1482.8 cm-1 (6.744 µm) at 120K to 1487.7 cm-1 (6.722 µm) at 80K) 0.
CW operation at O § 4.60Pm LN2-CW-DFB-10-2171 Wavelength [µm] 4.62 4.615 4.61 4.605 4.60 4.595 Normalized intensity 1 0.1 80K, 80K, 80K, 80K, 80K, 80K, 90K, 90K, 1.5 mm-long, 21 µm-wide laser CW operation at λ ≈ 4.60 µm 550mA 650mA 750mA 850mA 950mA 1.05A 1.0A 1.1A Single-mode emission: Side Mode Suppression Ratio > 25 dB (limited by the resolution of the FTIR) 0.01 Tuning range: ∆ν = 8 cm-1 at 2171 cm-1 (0.37%) 0.001 2164 Characteristics 2166 2168 2170 2172 2174 2176 (2167.
Continuous-wave FP QCL on Peltier RT-CW-FP-50-1080 6 80 -25°C 60 4 -20°C 50 3 -15°C 40 -10°C 30 -5°C 20 0°C 10 1.5 mm-long, 13 µm-wide λ ≈ 9.2 µm jth (-30°C) = 4.05 kA/cm2 2 1 0 0 0.2 0.4 0.6 0.8 1.0 1.2 Average power [W] Voltage [V] 70 -30°C 5 Iop < 1.2 A Uop < 6 V 0 1.4 Current [A] Page 39 of 51 Boston Electronics * QCL@boselec.com BH distributed-feedback QCLs W Wavel eng en gth [µm] 8.96 grating 680mA 100 n -In P P i - In 8.
THz applications New sources: R. Köhler et al., Nature 417, p.156, 2002. M. Rochat et al., Appl. Phys. Lett. 81 (8), p.1381, 2002. Terahertz applications: – Astronomy – Medical imaging – Chemical detection – Telecommunications for local area network (LAN) Page 41 of 51 Boston Electronics * QCL@boselec.com Terahertz sources THz QC laser based on a bound to continuum design, O § 87 Pm Structure grown at University of Neuchâtel (G. Scalari, L. Ajili, M. Beck and M.
Reliability of the devices Page 43 of 51 Boston Electronics * QCL@boselec.com Reliability of the devices: ageing Pulser QCL 2 30°C Power [mW] QCL 1 Voltage [V] Tmeasure = 30°C Current [A] QCL 3 Temperature controller Tageing = 130°C 10 Detectors 10 Slots Page 44 of 51 Boston Electronics * QCL@boselec.
Ageing: theory Conversion of lifetime using Arrhenius type relation: t ~ exp[E/(kT)] where: t is lifetime T temperature E=0.7 eV activation energy [H. Ishikawa et al., J. Appl. Phys. 50, 1979] (needs to be evaluated for QCL) The room temperature lifetime t1 (at T1 = 20°C and 70% of initial power) can be extrapolated by : t1 = t0 ⋅ e E 1 1 ⋅ − k T1 T0 with t0 is the measured lifetime at the ageing temperature T0 (here 130°C = 403K).
Production Page 47 of 51 Boston Electronics * QCL@boselec.
Production - lasers off the shelf Wavelength [µm] 20.0 10.0 7.0 1000 1500 5.0 4.0 2000 2500 3.0 Possible Need customization process Multimodes off the shelf DFB off the shelf 500 3000 Wavenumber [cm-1] for an up to date wavelength listing, contact us at: http://www.alpeslasers.ch Page 49 of 51 Boston Electronics * QCL@boselec.com List of products - prices Type Dutycycle Operating temp.
Conclusion / outlook Available products • pulsed DFB QCL on Peltier cooler in the range of 4.3Pm to 16.5Pm • LN2 continuous-wave DFB QCL in the range of 4.6Pm to 10Pm • continuous-wave FP on Peltier cooler at 9.1Pm Soon available • THz sources (LN2) Available end 2004 • continuous-wave DFB on Peltier cooler (already demonstrated: T. Aellen, S. Blaser, M. Beck, D. Hofstetter, J.Faist, and E. Gini, Appl. Phys. Lett. 83, p.1929, 2003) Page 51 of 51 Boston Electronics * QCL@boselec.
PRODUCTS Distributed Feedback Laser (Single mode) x Operation in pulsed mode x Two different mountings available: o TH mounting (bolt down) Size: 20 x 6 x 3.2 mm3 o SB mounting (clamp-holder) Size: 19 x 7 x 2 mm3 x Room temperature operation x Output power: Average: 2 - 10 mW o Peak: 100 - 500 mW x Beam divergence (full angle): o o o 60° perpendicular 40° parallel Lead time 2-8 weeks Available wavelengths: 5.3 - 6.0 µm and 10.0 - 10.
Fabry-Perot Laser (Multimode) x Operation in pulsed mode x Two different mountings available: o TH mounting (bolt down) Size: 20 x 6 x 3.2 mm3 o SB mounting (clampholder) Size: 19 x 7 x 2 mm3 x Room temperature operation x Output power: Average: 2 - 10 mW Peak: 100 - 500 mW x Beam divergence (full angle): o o o o 60° perpendicular 40° parallel Lead time 2-8 weeks Available wavelengths: 5.0 - 6.2 µm and 8.5 - 10.
Starter kit Equipment for operating Distributed-Feedback-Laser and Fabry-Perot-Laser. Overview: This kit contains: (1) Pulse generator, (2) connector cable to (3) pulse switcher, (4) low impedance line conducting pulses to (5) laboratory laser housing. Power supply of internal cooling elements via (6) connector cable by (7) temperature controller.
Laboratory Laser Housing - LLH x x x x x x x x Peltier cooled laser-stage inside, minimal temperature <-30°C Laser power supply by low impedance line from LDD Anti Reflection Coated (3.5 to 12 µm) ZnSe window. Exchangeable laser sub mount. Direct voltage measurement on the laser connection, AC coupled. PT-100 or NTC temperature measurement. Needs air or water-cooling. Temperature stabilization and power supply by TC51 x Size: 10cm x 5cm x 5cm Low impedance line x Length: 0.
Lead time 2 weeks LDD supply cable x Length: 2.0m Lead time 2 weeks Pulse Generator - TPG128 Two TTL 50 Ohm output Synchronization output Rise/fall time < 10 ns Pulse duration 20 to 200 ns Pulse repetition rate 10 kHz to 5 MHz Gate input Power supply 220V, 50-60 Hz This unit drives the LDD (duty cycle up to 20%) x Size: 22cm x 7cm x 13.5cm x x x x x x x x Lead time 2 weeks Temperature Controller - TC51 x x x x x x Temperature range: -35°C ..
x Size: 11.5cm x 22cm x 27.5cm Connector cable TC51 - LLH x x Length: 1.
APPLICATIONS Fields of applications: Quantum cascade lasers have been proposed in a wide range of applications where powerful and reliable mid-infrared sources are needed. Examples of applications are: Industrial process monitoring: Contamination in semiconductor fabrication lines, food processing, brewing, combustion diagnostics. Life sciences and medical applications Medical diagnostics, biological contaminants. Law enforcement Drug or explosive detection.
2.004 243 2.779 6800 4.255 69000 Approximate relative line strengths for various bands of the CO2 gas. Moreover, because of the long wavelength, Rayleigh scattering from dust and rain drops will be much less severe than in the visible, allowing applications such as radars, ranging, anti-collision systems, covert telecommunications and so on. As an example, Rayleigh scattering decreases by a factor 104 between wavelengths of 1µm and 10µm.
The advantage of the TILDAS technique is mainly its sensitivity. First of all, under good modulation condition, an a.c. signal on the detector is only present when there is absorption in the chemical cell. Secondly, this signal discriminates efficiently against slowly varying absorption backgrounds. For this reason, this technique will usually work well for narrow absorption lines, requiring also a monomode emission from the laser itself.
Photoacoustic detection has already been used successfully with unipolar laser, see - Paldus et al., Optics Letters ... Customers Our list of customers includes: Jet Propulsion Laboratory (USA), Vienna University of Technology (Austria), Fraunhofer Institute (Germany), Georgia Institute of technology (USA), ETHZ (Switzerland), Physical Sciences Inc. (USA): first QCL based product, Aerodyne (USA), Scuola Normale de Pisa (Italy), Orbisphere (Switzerland).
TECHNOLOGY General device characteristics How do I drive the device? As for any semiconductor laser, the performance of the device depends on the temperature. In general, unipolar lasers need (negative) operating voltage around 10 V with (peak-) currents between 1 and 5 A, depending on the temperature and the device. Around room temperature, that is the temperature range (-40..
Electrical model: In a simplified way, the device can be modeled, for electronic purpose, by a combination of two resistors and two capacitors. As shown by the above I-V curves, R1 increases from 10 to 20 Ohms at low biases to 1-3 Ohms at the operating point. C1 is a 100-pF capacitor (essentially bias independent) between the cathode and the anode coming from the bonding pads.
High duty cycle operation of a unipolar laser Typically, because of excess heat due to the driving current, unipolar lasers must be driven by current bursts with typically 10 ns rise time and a pulse-length of 100 ns. Some unipolar lasers may also operate in continuous wave (c.w.) at cryogenic temperatures, with a maximum operating temperature of 50 to 100 K depending on the design. Alpes Lasers specify c.w. operation on special request.
a) b) a) spectra of a long wavelength laser based on a diagonal transition b) spectrum of a short wavelength laser based on a vertical transition
Electrical tuning By driving the device with two different electrodes, wavelength and output power can be independently adjusted. Tuning ranges as large as 40 cm-1 at a peak power of 5 mW and a temperature of -10 °C have been obtained by Alpes Lasers. See literature for more details on this technique.
Emission spectra versus temperature for a DFB-UL. The device is driven at its maximum current. It must be stressed that because of this tuning effect, when operated in pulsed mode close to room temperature, the linewidth of emission is a strong function of quality of electronics driving the laser. The latter should optimally deliver short pulses (best 110 ns to obtain the narrowest lines) with an excellent amplitude stability.
(see figures below). A f#1 optics will typically collect about 70% of the emitted output power. Be careful that the collected output power will decrease with the square of the f-number of the collection optics. The mode is usually very close to a Gaussian 0,0 mode.
QCL FAQ List Frequently Asked Questions about QC laser systems from Alpes Lasers SA ($Id: alfaq.texi,v 1.4 2004/06/17 14:25:49 yargo Exp $) This FAQ should address the main questions arising for and from operation of CW and pulsed mode QC lasers from Alpes Lasers SA, especially in combination with the starter-kit. The information given herein is based on best knowledge, but since lasers can behave differently, no guarantee can be given that it will hold true in any case.
i Table of Contents 1 Mechanical and geometrical properties . . . . . . . . . . . . . . . . . . 1 1.1 1.2 2 1 1 1 1 1 Electrical and optical properties . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1 2.2 2.3 3 Geometry of QC lasers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.1 How are the axes of the laser defined, i.e. what is vertical? . . . . . . . . . . . How to handle a QCL . . . . . . . . . . . . . . . . . . . . . . . .
ii 4 Operating QCLs in continuous wave mode . . . . . . . . . . . . . . 10 4.1 4.2 5 General QCL questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5.1 5.2 5.3 5.4 6 available QC laser series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . How to measure QC laser emission?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General emission characteristics . . . . . . . . . . . . . . . . . . . . .
Chapter 1: Mechanical and geometrical properties 1 1 Mechanical and geometrical properties QC lasers from Alpes Lasers SA are mounted on special carriers, which require special handling and definition of geometrical orientation. 1.1 Geometry of QC lasers 1.1.1 How are the axes of the laser defined, i.e. what is vertical? The vertical direction is the so called growth direction. In practice, you have a device in front of you, it is mounted on a copper carrier.
Chapter 1: Mechanical and geometrical properties 2 1.2.2 How do I handle (carry) a QCL? The most delicate parts of a QCL are the laser chip itself and the bonds connecting it to the ceramic pads. Therefore the QCL should be touched only at the copper carrier (far from the laser chip and the bonds), or at the ceramic pads (again away from the bonds).
Chapter 2: Electrical and optical properties 3 2 Electrical and optical properties This chapter discusses electrical properties of pulsed and CW QC lasers; for special issues concerning CW operation, see Chapter 4 [CW mode], page 10. 2.1 Electrical limits 2.1.1 What is the maximum allowed duty cycle? This strongly depends on the laser. As a general rule, most lasers sold by Alpes Lasers SA are capable of being driven up to 10% duty cycle with pulse lengths up to 100ns.
Chapter 2: Electrical and optical properties 4 Pulsed mode devices have an impedance in the region of 5..50ohm up to about half the threshold current, then it decreases to the region of 0.5..5ohm. When operated at too high current, the impedance can rise again (a condition to be avoided in any case). 2.2.
Chapter 2: Electrical and optical properties 5 2.3.1 Mode characteristics The emitted mode is single lateral, and also single longitudinal for the DFB devices. The divergence is 60deg FWHM in the vertical direction and 10 to 20deg FWHM in the horizontal direction (see the images on our website at http://www.alpeslasers.ch/technology/Technology.htm). 2.3.1.
Chapter 2: Electrical and optical properties 6 These are highly approximative values; if you need well defined ones, ask for the needed values for a specific laser you are interested in.
Chapter 3: Starter kit (pulser, temperature controller etc) 7 3 Starter kit (pulser, temperature controller etc) This chapter discusses properties of the Starter kit, used for pulsed mode lasers. 3.1 Operation of TE cooler 3.1.1 What is the dissipated heat of a pulsed QC laser? Pulsed QC lasers in general work at threshold voltages of 9V. . . 12V and threshold currents of 1A. . . 3A, with maximum values of up to 13V and 10A. The peak power during operation therefore can vary in the range of about 10W. .
Chapter 3: Starter kit (pulser, temperature controller etc) 8 3.3.1 What are function and purpose of a bias-T circuit? 3.3.1.1 What is the function of the bias-T? The bias-T allows to apply a constant (DC) current to the laser in addition to the pulsed current (therefore a bias-T is useless in CW mode). The current is drawn from the external (user supplied) power supply through the laser. This current can be controlled electrically. Alpes Lasers SA specifies use up to of 0.
Chapter 3: Starter kit (pulser, temperature controller etc) 9 • Heating of the active zone will increase thermal stress of the laser, therefore the expected lifetime will decrease more rapidly compared to increasing the temperature of the laser submount and base in total. If operation at only a fixed wavelength is needed, this should be adjusted with the overall temperature control. • Too high a DC bias current can immediately destroy the laser due to catastrophic thermal roll-over.
Chapter 4: Operating QCLs in continuous wave mode 10 4 Operating QCLs in continuous wave mode For electrical properties, see Section 2.2 [Electrical properties], page 3. 4.1 Thermal properties The dissipated heat of a QC laser operated in CW mode is in the range of some Watts (operating voltage in the 8V. . . 12V range, current in the 0.5A. . . 1.5A range). Keep in mind that in general, the impedance of a QCL is decreasing with temperature! 4.
Chapter 5: General QCL questions 11 5 General QCL questions This chapter discusses some general properties of QC lasers, mainly concerning optical behavour. For additional information, See Chapter 2 [Electro-optical], page 3. 5.1 available QC laser series Alpes Lasers SA provides three types of single mode devices: RT-P-DFB-2-X designed for chemical sensing of atmospheric pressure gases in a room temperature (Peltier cooled) system.
Chapter 5: General QCL questions 12 Power meter To measure power, semiconductor power meters are used, in particular the combination of power head 2A-SH with meter AN/2 from OPHIR (http://www.ophiropt.com). Spectrometer Standard measurements are done with TRIAX320 monochromators from Jobin Yvon (http://www.jobinyvon.com), special (high resolution and CW) measurements with Nicolet 800 and 860 FTIR (http://www.nicolet.com).
Chapter 5: General QCL questions 13 repeated at a rate corresponding to 0. . . 3% for usual DFBs and up to 10. . . 20% for high power DFBs. At 10 ns pulse length, the line-width will be close to minimal in pulsed operation, less than 0.1/cm, and at 100 ns it will be larger, depending on the device. 5.3.4 What optical powers can be expected? See Section 5.1 [QCL series], page 11. 5.3.5 How precise should emission be specified? Normally, specification to 0.5/cm or 1nm should be sufficient.
Chapter 5: General QCL questions 14 5.4.4 How and how much does a FP-QCL tune? A FP-QCL tunes because of the shift in gain of the structure with temperature. This tuning is about twice as fast as the index tuning of DFB-QCLs, i.e about 1.3E-4/K (increasing temperature will result in increased wavelength). On a Peltier cooler like the one included in the Alpes Lasers SA starter-kit, the obtainable temperature span is about 60K (-30. . . +30degC). Therefore the central wavelength can be shifted by about 1.
Chapter 6: Commercial matters 15 6 Commercial matters 6.1 Laser and starter-kit delivery times Off-stock devices can be obtained within less than two weeks. For built-to-order devices, we offer 6 months lead time, due to the delicate nature of the fabrication process. This time can be reduced in case the needed wavelength requires only reprocessing of an existing laser crystal, and not redesign of a new one. Electronic equipment normally has delivery times of two to three weeks.
Chapter 7: Glossary and Abbreviations 16 7 Glossary and Abbreviations CW Continuous Wave; for lasers this means operation with DC current, generating uninterrupted emission. See Chapter 4 [CW mode], page 10. DFB Distributed Feed-Back; describing a laser with an etched grating close to its active zone, which acts as a filter, reducing overall gain for all but the wavelengths defined by the grating period. This technique allows to produce single-mode lasers also for pulsed mode operation.
Products Getting started RT-P-FP-2...50-X Q: How do I operate a QCL? A: A starter kit is proposed in order to Lasers designed for acqueous chemical sensing. - Room temp. operation - Pulsed - Multiple line emission - Single lateral mode - Far field 10°x60° FWHM - 2,5,10,20,50 mW average power - Wavelength off stock: 4.6, 5.2, 6, 10.35, 17-µm and many others, please ask (not all power rating are available). - Built to order from 3.
Bipolar Unipolar Products RT-P-DFB-2-X Lasers specifically designed for chemical sensing. - Room temp. operation - Pulsed - Single line emission - Single lateral mode - Far field 10°x60° FWHM - 2 mW average power - Wavelength off stock: 4.6, 5.2, 10.35, 17-µm and many others, please ask. - Built to order from 3.5 to 17 µm RT-HP-DFB-5,10,20-X Alpes Lasers CP 58 CH-2008, Neuchâtel Switzerland Tel +41 878 803 041 Fax +41 878 803 042 www.alpeslasers.ch info@alpeslasers.
