Laser Cooling in Semiconductors

woundcallousSemiconductor

Nov 1, 2013 (3 years and 9 months ago)

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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


Cooling Cycle

phonons

phono
ns

1

2

4

excited
state

ground
state

3

Laser

The concept of laser cooling in
semiconductors


Pump

Semiconductor

heterostructure



h


h

f

Valence band

Conduction band

E
g

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

Pump

semiconductor



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.



Refrigerant solid

fluorescence

heat sink

laser

cold finger

element


All
-
solid
-
state (rugged, compact)


No vibrations (no moving parts or fluids)


Efficient


For space
-
based sensors

Thank you