Transcript Semiconductor Lasers: Infrared to Blue Devices

Semiconductor
Lasers: Infrared to
Blue Devices
Jim Guido
Origins
Semiconductor lasers have existed for
about 40 years.
 First demonstrated by Robert N. Hall at
General Electric in 1962.

Motivation
Semiconductor lasers have a wide range
of useful applications.
 Many architectures exist for implementing
laser diodes.
 Devices scale with technology.

Basic Principles
Stimulated Emission

Electron distribution in a binary semiconductor (GaAs) is
N2
  ( E 2  E1) 
 exp

N1
kT


where N2 > N1 and E2 > E1 in order to receive the optical
amplification necessary for lasing action to occur.
Basic Principles
Resonant Optical Cavity



Causes an increase in optical intensity
via positive feedback.
Waves propagate by reflecting back and
forth between the two end mirrors.
For resonance to occur, the optical cavity
must satisfy the following condition

N   L
2

where N is an integer, and L is the length
of the optical cavity.
L > λ (typically) which leads to multiple lasing modes.
Basic Applications
Optical Storage Devices

CD-ROM/RW, DVD, HD-DVD, BLU-RAY
I/O Devices

Bar-code readers, laser printers, scanners
Telecommunications

Light sources to fiber optic networks
High-energy Devices

Gem-cutting, Laser Fusion
The Future?

Indirect Bandgap Devices
Why?
 Devices formed from silicon can have more
metal layers than their GaAs counterparts.
 Silicon is cheaper, and more prevalent.
 Semiconductor lasers formed from silicon might
make optical interconnects more feasible.
References
[1] “Laser diode.” Wikipedia. 28 Nov. 2006. Wikimedia Foundation, Inc. 16 Nov.
2006 http://en.wikipedia.org/wiki/Laser_diode
[2] “Stimulated Emission.” Wikipedia. 2 Dec. 2006. Wikimedia Foundation, Inc.
15 Dec. 2006 http://en.wikipedia.org/wiki/Stimulated_Emission
[3] Neamen , Donald A. Semiconductor Physics and Devices: Basic Principles.
New York: McGraw-Hill, 2003, pp. 653-661.
[4] Coffa, Salvatore. “Light From Silicon.” IEEE Spectrum. Oct. 2005: 44-49.