Transcript Li Weimen sol 2014 sm

Modeling and Design of Waveguides for
16 𝜇𝑚 Quantum Cascade Lasers
By Weimen Li, Ching-Yu Chen, and Claire Gmachl
With Funding Support
Provided by:
MIRTHE,
National Science
Foundation, and
Princeton Environmental
Institute
Dielectric
Gold Contact Layer
Glass Insulating Layer
Barrier Layer(s)
Cladding Layer(s)
Active Region
Cladding Layer(s)
Barrier Layer(s)
InP Substrate
What is MIRTHE?
• MIRTHE stands for Mid-Infrared
Technologies for Health and the
Enviroment.
• It’s aim is to develop Mid-Infared trace gas
sensing systems based on cutting edge
infrared technology.
• Developments are used to detect minute
amounts of chemicals in the environment.
Source: http://www.mirthe-erc.org/mirthecenter/about/
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Development of a 16 𝝁𝒎 QC laser
• What is a 16 𝜇𝑚 QC Laser?
– 16 𝜇𝑚 is the wavelength of the laser light.
– “QC” stands for Quantum Cascade, which
describes the mechanism of how the laser
operates.
"Cascade transitions" by Alexander Valavanis, University of Leeds.
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Development of a 16 𝝁𝒎 QC
laser
• Why develop a QC laser at 16 𝜇𝑚?
– All elements, and gases in particular, will
absorb light at specific wavelengths.
– This absorption spectra can be measured
using sensors.
– Infrared light sources and sensors can be
used to form detectors for gases that absorb
at these wavelengths.
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My Contribution
1. Development of Client Software in
MATLAB Code.
2. Implementation of theoretical models to
anticipate waveguide characteristics.
3. Design of a waveguide based off of
modeling results.
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Client Software
Purpose: Allow for modular input of new models and ease of accepting waveguide
designs.
CLIENT:
1 PHONON LOSS
MODEL
Inputs:
Different designs can be conceived and
saved.
Design 1
Design 2
Design 3
FREE CARRIER
LOSS MODEL
Output:
KNOWN
PARAMETER INPUT
Mode confinement factor, waveguide loss, mode
intensity graph, effective mode index, refractive
indices of each layer.
POSSIBLE OTHER
MODELS
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Waveguide Modeling
Challenge: Waveguide losses are significantly increased at
higher wavelengths.
Solution: Model phonon absorption losses and design a
waveguide based on optimal model parameters.
Waveguide Design
Results:
• Type: Dielectric
• Growth Height: 7.27 𝜇𝑚
• Confinement Factor: >55%
• Loss coefficient: ~42 𝑐𝑚^(−1)
• Effective Mode Index:
3.2076+0.0053465i
Laser P175 (SP) Laser P206R1 (DE) Laser A1162 (DE)
Wavelength (𝜇m)
14.7
14.7
4.9
Experimental Loss (cm-1)
63.9
29.6
4.9
Total Model Loss (cm-1)
% Difference
43.8
31%
37.8
-28%
3.4
31%
Drude Model Loss (cm-1)
38.2
33
2.6
1 Phonon Model Loss (cm-1)
5.6
4.8
0.8