Antimony Based High Power 3-5 μm Lasers

High Power Double Heterostructure Lasers

Double heterostructure (DH) lasers based on the InAs/InAsSb/InAsSbP material system were grown by low-pressure Metal Organic Chemical Vapor Deposition (LP-MOCVD) for high power lasers emitting with 3.1 ≤ λ ≥ 3.4 μm. The lasers exhibitedthe lowest threshold current density reported of only < 40 A/ cm² at 90 K and high differential efficiencies of up to 90%. Laser bars consisting of four 100 μm stripes exhibited a maximum peak output power of 6.7 W. This registers the highest output power in this wavelength range. Furthermore, optimizing the heat dissipating properties of these lasers allowed over 450 mW per 100 μm to be obtained under continuous operation.

 

Light output power versus continuous and pulsed injected current (PI) for the InAsSb/InAsSbP DH laser.

Easily Tunable Superlattice Lasers

In order to increase the emission wavelength to beyond 3.4 μm, the InAsSb active layer must be thinner (less than 20 nm) and have an increased amount of Sb. This is accomplished by fabricating lasers with multiple quantum well (MQW) or strained-layer superlattice active regions. MQW lasers fabricated with 10 compressively strained InAsSb wells allow emission wavelengths between 3.5 and 3.7 μm. Lasers with apertures of 100 μm were fabricated and demonstrated output powers of 1 W in pulse mode at 90 K. The differential efficiency was measured to be over 70% up to 155 K. Such high values of differential efficiency for the wide range of temperature, to the best of our knowledge, had never been obtained fromlasers based on conventional interbandtransition for λ > 3.5 μm.

High Power Superlattice Lasers

In order to increase the emission wavelength to beyond 3.4 μm, the InAsSb active layer must be thinner (less than 20 nm) and have an increased amount of Sb. This is accomplished by fabricating lasers with multiple quantum well (MQW) or strained-layer superlattice active regions. MQW lasers fabricated with 10 compressively strained InAsSb wells allow emission wavelengths between 3.5 and 3.7 μm. Lasers with apertures of 100 μm were fabricated and demonstrated output powers of 1 W in pulse mode at 90 K. The differential efficiency was measured to be over 70 % up to 155 K. Such high values of differential efficiencyfor the wide range of temperature, to the best of our knowledge, had never been obtained from lasers based on conventional interband transition for λ > 3.5 μm.

 

Fabrication and packaging technologies have been developed at CQD for these lasers.

Finally the first midinfrared SLS injection lasers have been fabricated with InAs/InAsSb, InAsP/InAsSb, and InAsSb/InAsSb superlattices. Although complex, SLS lasers benefit from better optical confinement and more emission wavelength flexibility than a DH laser and a larger gain region than a MQW laser. Another advantage that these superlattice lasers have is the reduction of non-radiative recombination (Auger) mechanisms which are inhibited by the large number of interfaces within the active region. Lasers employing 100 period InAs/InAsSb operated between 3.8 and 4.0 μm with record powers of up to 1 W and 300 mW in pulsed and continuous modes at 90 K. Using an 80 period InAsP/ InAsSb superlattice active region, lasers emitting at 4.0 μm and operated with powers as high as 546 mW and 94 mW in pulsed and continuous modes respectively. Finally, using a 100 period InAsSb/ InAsSb superlattice, lasers emit between 4.2 and 4.8 μm with powers as high as 460 mW. This is the longest reported emission from lasers based on interband transitions.

 

A record low threshold current of only 104 A/cm2 at T=77 Kelvin was measured.

Last Updated 01/31/2007

Northwestern University