Semiconductor Lasers: Infrared to Blue DevicesJim 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 PrinciplesStimulated Emission

Electron distribution in a binary semiconductor (GaAs) is

where N2 > N1 and E2 > E1 in order to receive the optical amplification necessary for lasing action to occur.

kT

EENN )12(

exp12

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

where N is an integer, and L is the length of the optical cavity. L > λ (typically) which leads to multiple lasing modes.

LN

2

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 DevicesWhy? 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.