Abstract
This feature issue presents recent progress in long-wavelength photonics, focusing on wavelengths that span the mid-infrared (3-50 µm), the long-wavelength infrared (30-60 µm), and the terahertz (60-300 µm) portions of the electromagnetic spectrum. The papers in this feature issue report recent progress in the generation, manipulation, detection, and use of light across this long-wave region of the "photonics spectrum," including novel sources and cutting edge advances in detectors, long-wavelength non-linear processes, optical metamaterials and metasurfaces, and molecular spectroscopy. The range of topics covered in this feature issue provide an excellent insight into the expanding interest in long-wavelength photonics, which could open new possibilities for basic research and applications in industries that span health, environmental, and security.
Highlights
Vol 28, No 9 / 27 April 2020 / Optics Express 14169Mid-infrared, long-wave infrared, and terahertz photonics: introductionRAVINDER K
While the visible spectral region is defined by the International Organization for Standardization (ISO) as wavelengths in the 380–780 nm spectral range, the infrared spectral region consists of wavelengths beyond the long wavelength edge of the visible spectrum, namely all wavelengths in the 780 nm – 1 mm (1000 μm) range, and is rigorously subdivided into the IR-A (780 nm -1.4 μm), IR-B (1.4 μm - 3 μm), and IR-C (3 μm - 1000 μm) bands, the latter being further subdivided into the mid-infrared (MIR), 3 μm – 50 μm, and the far-infrared (FIR), 50 μm - 1000 μm, bands [ISO 20473, 2007]
We have treated the exact nomenclature and frequency band designations in this Feature Issue as somewhat arbitrary, and have deferred to the band designations used by the authors; the general focus of this Feature Issue is on “long wavelength photonics at wavelengths longer than 2 μm”, with the spirit of long-wavelength photonics implying use of wavelengths in the “mid-infrared and beyond” all the way upto Terahertz frequencies corresponding to the “borderline” of what usually constitutes microwaves, i.e., up to ultralong wavelengths and ultralow frequencies that use technologies and techniques that are usually very different than those used in conventional photonics
Summary
Unlike the ultraviolet and visible regions of the electromagnetic spectrum, which have been studied intensely over the last few centuries, starting with early experiments on the science and engineering of visible light by Newton, the infrared region of the electromagnetic spectrum is in a relative stage of infancy. While the visible spectral region is defined by the International Organization for Standardization (ISO) as wavelengths in the 380–780 nm spectral range, the infrared spectral region consists of wavelengths beyond the long wavelength edge of the visible spectrum, namely all wavelengths in the 780 nm – 1 mm (1000 μm) range, and is rigorously subdivided into the IR-A (780 nm -1.4 μm), IR-B (1.4 μm - 3 μm), and IR-C (3 μm - 1000 μm) bands, the latter being further subdivided into the mid-infrared (MIR), 3 μm – 50 μm, and the far-infrared (FIR), 50 μm - 1000 μm, bands [ISO 20473, 2007] Despite these formal designations for different spectral regions by ISO, the general research literature on infrared optics and photonics often uses different designations and different range definitions for various regions of the IR spectrum, including the MIR. We have treated the exact nomenclature and frequency band designations in this Feature Issue as somewhat arbitrary, and have deferred to the band designations used by the authors; the general focus of this Feature Issue is on “long wavelength photonics at wavelengths longer than 2 μm”, with the spirit of long-wavelength photonics implying use of wavelengths in the “mid-infrared and beyond” all the way upto Terahertz frequencies (corresponding to wavelengths of several 100 μm or frequencies as low as 0.3 THz) corresponding to the “borderline” of what usually constitutes microwaves, i.e., up to ultralong wavelengths and ultralow frequencies that use technologies and techniques that are usually very different than those used in conventional photonics
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