1. Mid Infrared Detectors
Presentation by
Ruqayyah Askar
PHYS 689
April 27, 2018

2. Outline Introduction General principles Historical overview
Types of IR detectors
Current IR technologies
Parameters of IR Detectors
Emerging Technologies
Applications of IR Detectors

3. Interest in Infrared Spectrum
A. Rogalski, Infrared Detectors, Second Edition, Boca Raton: CRC Press (2010).

4. Interest in the Infrared Spectrum
Molecules has large absorption cross- sections in the mid- infrared region of the spectrum.
Figure. HITRAN simulation of absorption bands of various molecules in the 3-5 µm spectral region. All species are plotted with identical relative concentration. Spectral overlap limits the choices of interference-free absorption lines.
I. T. Sorokina, K. L. Vodopyanov, Appl. Phys. 89, (2003).

5. General Principles
The Electromagnetic Spectrum

6. General Principles The Electromagnetic Spectrum
A. Rogalski, Infrared Detectors, Second Edition, Boca Raton: CRC Press (2010).

7. Historical Overview
Initial discovery of infrared radiation by the German astronomer F. W. Herschel in 1800, using thermometers.
The German physicist Th. J. Seebeck discovered the first thermocouple in 1821.
Sir Frederick William Herschel ( )
Thomas Johann Seebeck ( )

8. Langley‘s Bolometer (1881)
Historical Overview
In 1829, the Italian physicist L. Nobili constructed the first thermopile, which was modified later by Melloni in 1833.
The bolometer follows in 1881 with more sensitivity.
Nobili‘s Thermopile, Virtual Museum
Melloni‘s Thermo-multiplier (1833)
Langley‘s Bolometer (1881)
Privat-Deschanel, "Elementary treatise on natural philosophy," Augustin , ( ).
S. P. Langley, “The Bolometer," Nature Publishing Group, (1881).

9. Historical Overview
In 1873, selenium was used in an experiment by an English electrical engineer W. Smith, after he discovered the photoconductive effect.
Case developed the first IR photoconductor in 1917 with high responsivity.
Willoughby Smith

10. Historical Overview Cs-O-Ag phototube appeared in 1930.
No further development until about 1940.
Lead Sulfide ( PdS ) was discovered as a photoconductive with response up to 3 µm by Kutzscher in Germany.
First practical IR detector is based on PbS.
Cashman showed that the lead salt family ( PbSe and PbTe) has the promise as IR detectors.

11. Historical Overview
Lead Sulfide ( PdS ) photoconductors manufactured in Germany in about 1943, and produced in the US and England (1944, 1945).
After discovery of transistor in the early 1950s, the first extrinsic photoconductive detectors were developed.
Advances in narrow bandgap semiconductors for more sensitivity.
III-V compound semiconductor family was discovered. InSb was the first material.
The development of mercury-cadmium-telluride (HgCdTe) in by Lawson and co-workers.

12. Historical Overview
Photolithography was available in the early 1960s, and was applied to make IR detector arrays.
In 1967, first paper on extrinsic Si detector was published by Soref.
Extrinsic Si was considered after Boyle and Smith invented the charge-coupled devices ( CCDs).
In the 1980s, the second generation of HgCdTe infrared systems was developed with low power dissipation.
A. Rogalski, Infrared Detectors, Second Edition, Boca Raton: CRC Press (2010).

13. Types of IR Detectors The two main types of IR detectors:
Thermal detectors:
- Operate based on detecting thermal effects of incident
IR radiation.
- Low coat and low performance.
Photonic detectors:
- Incident IR radiation causes intrinsic or extrinsic
electronic excitations.
- High cost and high performance
Infrared Thermometer - MLX90614
PDA20H PbSe Detector µm

14. Current IR Technologies
Currently, high performance IR technologies are mainly based on
- Grown structures of small bandgap mercury-cadmium-
telluride ( MCT )
- Indium-antimonide ( InSb )
- GaAs based quantum well infrared photoconductors (QWIPs)
The material is chosen based on the application and the wavelength.

15. Current IR Technologies
The energy band diagram of MCT and QWIP showing electronic transitions.
A. Karim and J. Y. Andersson, IOP Conf. Ser, Mater. Sci. Eng. 51, (2013)

16. Parameters of IR Detectors
Responsitivity (R).
Noise equivalent power (NEP).
Detectivity (D).

17. Emerging Technologies
The demand is for lower cost high performance detectors.
Some of the emerging technologies include:
- Quantum dot infrared photodetectors (QDIPs)
- Type-II strained layer super-lattice.
- QDIPs with type-II band alignment.

18. Emerging Technologies
Figure:
Comparison of the detectivity of various available detectors when operated at the indicated temperature.
C. Tan and H. Mohseni, Nanophotonics 7(1), (2017).

19. Emerging Technologies
Table:
Summary of the advantages and the disadvantages of the current nanostructure-enhanced IR photodetectors.
C. Tan and H. Mohseni, Nanophotonics 7(1), (2017).

20. Emerging Technologies
Michelson Interferometer-based technologies
Interferometric autocorrelation setup in our laboratory.

21. Emerging Technologies
Dual comb Infrared Laser Spectroscopy
a) Time domain of dual comb spectroscopy, b) Frequency domain of dual comb spectroscopy.
A. Schliesser, N. Picqué, T. W. Hänsch, Nature Photonics 6, (2012).

22. THANK YOU