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

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

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

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, 445-516 (2003).

General Principles The Electromagnetic Spectrum

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

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 (1738-1822) Thomas Johann Seebeck (1770-1831)

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 1821-1883, 187376 (1873-76). S. P. Langley, “The Bolometer," Nature Publishing Group, 14-16 (1881).

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

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.

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 1959 by Lawson and co-workers.

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).

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 1.5-4.8 µm

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.

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, 012001 (2013)

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

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.

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), 169-197 (2017).

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), 169-197 (2017).

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

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, 440-449 (2012).

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