Laser Cooling in Semiconductors
Chengao Wang
Optical Science and Engineering,
Department of Physics & Astronomy, University of New Mexico
Historical Review
1929: The concept of laser cooling was established.
1960: Laser was invented.
1995: Laser cooling was first observed in ytterbium-doped glass.
????: Laser cooling in semiconductors is achieved.
Significance
Heating is a major problem in semiconductor devices.
Optical refrigerator using laser cooling will be free of vibration, mechanically robust and compact.
It has far reaching implications in the area of optical detection systems and optoelectronic devices.
Purpose
invent a practical all-solid-state optical refrigerator to cool semiconductors using laser cooling.
We hypothesize that laser cooling in semiconductors can achieve temperatures ~10K and below
Overview of Methodology
1. Develop a comprehensive theoretical model of laser cooling in semiconductors.
2. Grow new semiconductor materials optimized for laser cooling using MOCVD
3. Demonstrate experimentally the theory of laser cooling in semiconductor devices.
4. Build prototype optical refrigerator in semiconductors.
The concept of laser cooling
The concept of laser cooling in semiconductors
Step 1: Develop a comprehensive theoretical model of laser cooling in semiconductors.
Two key issues, luminescence trapping and red-shifting, have not been addressed in the current theory and these issues will frustrate our attempts to achieve semiconductor net cooling
Luminescence Trapping
Total internal reflection
Luminescence red-shift
Step1: Deliverable
understanding of which materials are optimum for laser cooling in semiconductors.
predict the possible designs of the future optical refrigerators.
Step 2: Use MOCVD to grow new semiconductor materials
InGaP/GaAs Heterostructures have been predicted to be good candidates for laser cooling in semiconductors.
perform microscopic analysis of each material in order to optimize the materials for laser cooling.
Step2: Deliverable
optimal materials that have a good chance of achieving net cooling.
Step 3: Demonstrate experimentally the theory of laser cooling in semiconductor devices
Do experiment to prove laser cooling in semiconductors
Step3: Deliverable
proof of net cooling in semiconductors
reevaluating our theory about laser cooling in semiconductors and further optimizing the materials.
Step 4: Build prototype optical refrigerator in semiconductors.
In order to build a practical devise, we should first solve some engineering issues.
After making the preliminary optical refrigerator, we may try to make it more compact and efficient.
Step4: Deliverable
an infant machine for practical applications.
The Goal: An All-Solid-State Cryocooler
The research involve all fundamental physics and engineering issues of laser cooling in solids that will pave the way for the development of a practical all-sold-state optical cryocooler.
All-solid-state (rugged, compact)
No vibrations (no moving parts or fluids)
Efficient
For space-based sensors
Thank you