NGS-13, Guildford UK, July 2007

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1 NGS-1, Guildford UK, July 7 Semiconductor light emitters for mid-ir spectral region -based Quantum Cascade Room temperature operated type-i QW -based light emitters with wavelength up to.4um L. Shterengas, G. Kipshidze, G. Belenky S. Suchalkin, D. Donetsky Dilute-nitride Type-I Strain compensated QCL Type-II 1µ µ µ 4µ µ Number of Photons (W/eV) 1 C 1.um (ev) QW -based.um (.ev) QW µm -based high power diode lasers demonstrate lower threshold current densities than 1.-1.µm diodes. High power RT operated type-i QW -based lasers.µm high power linear laser array E g =.1 APL 4 ns, 1 khz uncooled 1 E g =.1 Al Al Waveguide - % Al Cladding - 9% Al.... Broadened waveguide. Power (W) 1 1 CW, 18 C A...4. us, Hz Wall-Plug Efficiency (%)....µm.. CW Power (W) SST T coolant =1-1 C. High power lasers at.,.7 and.8 µm.µm.7µm.8µm 4 8 CW Efficiency decreases with wavelength E g =.1...7µm.µm.8µm... CW Power (W) SST T coolant =1-1 C. Temperature dependence of laser efficiency.µm.7µm.8µm 4 8 CW 1 In /.14 As. In /.19 As. In /. As 1.% 1.8% Normalized External Efficiency..µm at RT.7µm at RT.8µm at RT As 14% As 19% As % % Temperature (K) Compressive improves hole confinement NGS-1, Guildford UK, July 7

2 NGS-1, Guildford UK, July 7 E g = %..-.4µm lasers with heavily ed active region. % immiscibility gap. Comp. % In.7.1 CW 1W Comp. 1.7% In Hole confinement is improved by ~7meV (Krijn, SST 1991) - Strain induced DOS modification is marginal Effect of the active region on laser threshold Power (mw) 1 1 l=.mm C 1mm,1um,AR/HR 1um, AR/HR C,ns/1kHz ~1mA ~ma -1.7% -%. Threshold current density is decreased twofold Pump 1nm Carrier lifetime in heavily ed QWs Emission. µm Normalized PL Intensity % 1.7% Delay Time (ns) Carrier lifetime is similar for both laser structures RT C Strain -% Sp. nm ma Modal gain spectra C Strain -1.7% Sp. 4nm 1mA Optical loss are 18- cm -1 (internal loss -8 cm -1 ) for both structures High differential gain in heavily ed QWs Hole confinement in. µm -based diode lasers Comp. % In.7.1 Comp. 1.7% In.7 8 Peak % -% 1 1 Current Density (A/cm ) Differential gain is increased nearly three times J th ~ A/cm J th ~ 1 A/cm Dif. Gain ~ 1 cm -1 /A Dif. Gain ~ cm -1 /A Krijn, SST 1991 Compressive Strain Valence Band Offset % ~ 1 mev 1.7 % ~ mev How well models predict valence band offsets? NGS-1, Guildford UK, July 7

3 NGS-1, Guildford UK, July 7 Estimated hole confinement is ~ 1meV W-QW -based optically pumped lasers In Ga In. Ga As.18.9 Experiment to determine the role of carrier confinement hole-qw In W-QW In What is the nature of the strong temperature sensitivity of the type-ii W-QW laser operation parameters? electron-qw R. Kaspi et al, APL Ultra-fast photoluminescence up-conversion Capture of electrons and holes in W-QWs PMT Spectrometer TRIAX sample h(v mid-ir +v Nd ) nonlinear crystal (PPLN, KNbO ) dichroic filter hv mid-ir hv mid-ir time Nd:glass, 1nm 1fs,1MHz h(v mid-ir+v Nd) Delay line max 1ns PUMP In In Normalized PL Intensity Wavelength (µm) K 1 4 Time (ps) Hole confinement of ~ mev leads to carrier delocalization at room temperature QW K 1K K High power.4µm heavily ed (1.%) diode lasers CW room temperature operation: PCE = 17.% Power (W) APL 7 CW, T=18 C epi-down 1mm 1mm mm mm A 1 1 Power Conversion Efficiency (%) Normalized PL. High power.4µm heavily ed diode lasers Carrier Lifetime ~ ns QW PL decay K 1 4 Time (ns) Peak Modal Gain per QW (cm -1 ) um 1.7% Peak modal gain -based.4um 1.%.um % 1.um C ns/1mhz 1 1 Current Density per QW (A/cm ) Heavily ed -based lasers demonstrate high differential gain and low threshold current density NGS-1, Guildford UK, July 7

4 NGS-1, Guildford UK, July 7 -based type-i QW emitters with λ above µm In-rich ed QWs Al-rich Al waveguide In ~ %, As ~ 1% In ~ %, As ~ % based type-i QW light emitting diodes at.4µm 4% Al in barrier QW % IR image of the LED output Al AlS b -. Energy (ev) E V (In. Ga. As..7 ) Al % Al % Al % E V (Al) p-contact epi n- n-contact Light out Power (a.u.). 1. C ns/1mhz Current Density (ka/cm ) Si N 4 -based type-i QW light emitting diodes at.µm Flat p-contact -based type-i QW lasers for above µm region epi E g =.1 n-. Photoluminescence (c/s) 4 n-contact Lifetime ~ps Light out C K.um LED Time (ns) EL power (mw). LED 4x, duty cycle % wavelength (um) 1 K 1 K K K 4 K K 8 K K.... ~µm.-.4µm immiscibility gap. % Al in barrier QW 1. % p-clad overlap ~1% -based type-i QW lasers operating near µm at RT Peak Power (mw/facet) 1 1 C C T ~ K Ext. eff. ~ 1% C n-down, 1um, mm, uncoated 1ns/1kHz 1 4 Peak 1 Voltage (V) Optical gain and loss near µm int. loss 1-1 cm -1 int. eff. ~% mA - 1 C, ns/1mhz n-down 1um, mm, uncoated NGS-1, Guildford UK, July 7

5 NGS-1, Guildford UK, July 7 Summary. µm -based lasers demonstrate high differential gain. Hole confinement is improved in heavily ed QWs. Differential gain is further increased in lasers with heavily ed active region leading to reduced threshold current densities. Room temperature operated type-i QW -based light emitting diodes with electroluminescence peak at.4um were fabricated. Supported by United States Air Force Office of Scientific Research NGS-1, Guildford UK, July 7