Quantum Cascade Laser

PH413

Lecture 23 Lecture 23

29.09.11

Transition schemes

InterbandInterband

Intersubband Miniband

Excitonic

Time-line of QCL development

Original concept and theoretical prediction

Kazarinov, R.F; Suris, R.A. ,"Possibility of amplification of electromagnetic

waves in a semiconductor with a superlattice". Fizika i Tekhnika

Poluprovodnikov 5, 797 (1971)

QCL discoverers

First QCL

Bipolar vs unipolar laser

QCL

Characteristics of QCL

�Wavelength determined by layer thickness rather than by material

composition

�All mid-infrared spectrum covered by the same material

�Each electron creates N laser photons in traversing an N-stage

cascaded structure (N = 20 - 75)cascaded structure (N = 20 - 75)

�Intrinsically high power lasers

�High reliability: low failure rate, long lifetime and robust fabrication

Dimensions

Interesting facts

�Laser wavelength covers entire range from 3.4 to 17 microns

�High peak power (0.5 W) at room temperature in pulsed mode

�High power (0.2 W) at liquid-nitrogen temperature in continuous mode

�High spectral purity (single-mode laser)

�Wide single-mode tuning for high resolution spectroscopy

�Demonstration of gas sensing capability

Applications

�Environmental sensing and pollution monitoring

– point sensors

– LIDAR(Light Detection and Ranging); open air

�Industrial process control

�Automotive

– combustion control, catalytic converter diagnostics

– collision avoidance radar, cruise control

�Medical applications

– breath analysis; early detection of ulcers, colon cancer, etc.

�Military and law enforcement

Detection of NO

1889 1890 1891 1892 1893 1894 1895 1896

0,00E+000

5,00E-021

1,00E-020

1,50E-020

2,00E-020

2,50E-020

3,00E-020

1895,19

1894,15

1893,86

1890,91

1890,71

NO

H2O

cm

2/m

ole

cule

wavenumber (cm-1)

1889,56

600

700

800

Hitran database

Asorption

Power ~ 2 mW , λλλλ ~ 5.29 µm

1889 1890 1891 1892 1893 1894 1895 1896

0

100

200

300

400

500

6001894,15

(NO)

1895,19

(H2O)

1893,86

(NO)

1890,70(NO)

1890,91(NO)

absorp

tion (

a.u

.)wavenumber (cm

-1)

1889,56(H2O)

1889 1890 1891 1892 1893 1894 1895 1896

800

1000

1200

1400

1600

1800

2000

2200

1890,91 (NO)1893,86 (NO)

1895,19 (H2O)

absorp

tion (

a.u

.)

wavenumber (cm-1)

1889,56 (H2O)

Asorption

spectrum of

NO in cell

Absorption

spectrum of NO

interacting with

evanescent field

QC microdisk laser