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№1 слайд![Quantum Cascade Laser](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img0.jpg)
Содержание слайда: Quantum Cascade Laser
№2 слайд![What kind of a laser is this](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img1.jpg)
Содержание слайда: What kind of a laser is this Quantum Cascade Laser ?
This is a semiconductor laser.
But the characteristics of this laser are different from the conventional semiconductor lasers.
№3 слайд![How do conventional](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img2.jpg)
Содержание слайда: How do conventional semiconductor
lasers work ?
A semiconductor absorbs light when electrons are excited from the valance band to the conduction band.
Light is emitted when those electrons drop into the valance band.
№4 слайд![Construction of the](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img3.jpg)
Содержание слайда: Construction of the conventional semiconductor laser
It has the active region which consists of two semiconductor materials forming a p-n junction
The injected electrons and holes in the active region recombine and create photons.
№5 слайд![Disadvantage of the](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img4.jpg)
Содержание слайда: Disadvantage of the conventional semiconductor laser
The band gap decides the wavelength of the laser. so to get the laser with different wavelength we have to choose a different material.
once an electron has emitted a laser photon by jumping from the upper to the lower energy level, it remains in the valence band.
№6 слайд![how quantum cascade laser](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img5.jpg)
Содержание слайда: how quantum cascade laser differs ?
QC lasers rely only on the one type of carrier, they are the electrons.
So they are also called the unipolar lasers.
Photon emission therefore relies on intraband transitions between quantized conduction band states in coupled quantum wells.
№7 слайд![Quantum wells Quantum wells](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img6.jpg)
Содержание слайда: Quantum wells
Quantum wells are ultra thin sandwiches of two different semiconductors.
A quantum well is essentially a semiconductor with relatively low band gap energy sandwiched between semiconductor layers with high band gap energies
the thickness is typically a few nanometers, and electrons are confined primarily to the center part of the sandwich.
№8 слайд![](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img7.jpg)
№9 слайд![](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img8.jpg)
№10 слайд![](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img9.jpg)
№11 слайд![](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img10.jpg)
№12 слайд![characteristics Wavelength](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img11.jpg)
Содержание слайда: characteristics
Wavelength determined by thickness rather then by the material.
All mid infrared covered by the same material. This important spectral range has so far been accessible mainly with relatively unreliable and expensive lead salt based diode lasers.
Each electron creates N photons when it traverse N stage cascade structure.
High power lasers.
Low failure rate, robust fabrication and long life time.
№13 слайд![](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img12.jpg)
№14 слайд![](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img13.jpg)
№15 слайд![](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img14.jpg)
№16 слайд![Applications Environmental](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img15.jpg)
Содержание слайда: Applications
Environmental sensing and pollution monitoring- point sensors, LIDAR
Industrial process control.
Automotive- cruise control, collision avoidance radar.
Medical- breath analyzer, early detection of ulcers, colon cancer
Military applications.
№17 слайд![Thank you](/documents_6/5e6ac86f5b45e61282ff452fedbe2bd4/img16.jpg)
Содержание слайда: Thank you