Reminder: Oral Exam Announcement: Tomas Sarmiento (Tuesday Oct. 23, 2PM, Allen-X Auditorium)

Tomas Sarmiento tsarmie at
Mon Oct 22 23:01:06 PDT 2012

GaAs-based 1550 nm GaInNAsSb lasers 

Tomas Sarmiento 
Department of Electrical Engineering 
Stanford University 

Advisor: James S. Harris 

Tuesday, October 23, 2012 
2:00 PM (Refreshments served at 1:45 PM) 
Allen-X Auditorium (formerly CIS-X Auditorium) 

Low-cost, long-wavelength light sources are indispensable for the widespread deployment of fiber-to-the-home networks. Vertical cavity surface emitting lasers (VCSELs) are ideal for these applications due to their high fiber-coupling efficiency, low power consumption, simple packaging and wafer-scale manufacturability. In particular, VCSELs emitting in the C-band (1530-1565 nm) are highly desirable given that the fiber optical loss is minimal in this wavelength range. High-performance 1550 nm InP-based VCSELs using various distributed Bragg reflector (DBR) technologies have been demonstrated, but these approaches generally require complex and extensive processing. In contrast, GaAs-based VCSELs can be processed in a simple and robust way by exploiting the superior material properties of Al(Ga)As/GaAs DBRs and the oxidation of AlAs layers for electrical and optical confinement. 

Dilute nitride GaInNAsSb alloys emitting in the 1200-1600 nm wavelength range can be grown coherently on GaAs substrates. Despite significant challenges in the growth of such highly-mismatched alloys, our group has demonstrated GaInNAsSb lasers with relatively low threshold current densities. In this talk, I will describe recent progress on the development of GaInNAsSb lasers. Optimization of the growth and annealing conditions enabled a four-fold enhancement of the photoluminescence efficiency of GaInNAsSb quantum wells. In addition, incorporation of GaAsP barriers significantly improved the temperature stability of the lasers. These growth advances enabled the realization of the first electrically-pumped GaInNAsSb VCSELs emitting in the C-band that operate at and above room temperature. 

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