DFB激光器.ppt

DFB激光器.pptDistributed Feedback Lasers Overview
Mike Huang
EE 290F
February 17, 2004 [Tuesday]
Semiconductor Lasers
I (pump current)
Add mirrors to provide optical feedback
Add optical guiding to improve efficiency
Optical Cavity (plane waves) [1]
Transmission of the optical cavity
Transmission as function of the electrical length
for different reflectivities (R) [1].
Maximum transmission for = q
Cavity with gain: R  G().R
Threshold Condition
Solve for gain 
(a) gain profile [3].
(b) intensity spectrum [3].
Single Longitudinal Mode Oscillation
Shorter cavity [VCSEL]
increase mode spacing
wider spectral width
Injection of external light
careful tuning
External coupled cavity
mechanical vibration, temperature and pressure changes
Diffraction grating inside the laser structure [DFB]
Laser Spectra
>100
~3
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Gain
Free Spectral Range
DFB and DBR lasers [3]
DFB DBR
HR coating
AR coating
Cross section of DFB Lasers
Laser output direction
Edge-Emitting Lasers:
Fabry-Perot (FP) Lasers
DFB (distributed feedback) Lasers
Vertical Cavity Surface Emitting Lasers (VCSEL)
Typical dimesion:
2 um x 500 um 5 um x 5 um