The mid-IR spectroscopic properties of doped low-phonon and crystals grown by the Bridgman technique have been investigated. Using optical excitations at and , both crystals exhibited IR emissions at , , , and at room temperature. The mid-IR emission at 4.5 µm, originating from the transition, showed a long emission lifetime of for doped , whereas doped exhibited a shorter lifetime of . The measured emission lifetimes of the state were nearly independent of the temperature, indicating a negligibly small nonradiative decay rate through multiphonon relaxation, as predicted by the energy-gap law for low-maximum-phonon energy hosts. The room temperature stimulated emission cross sections for the transition in doped and were determined to be and , respectively. The results of Judd–Ofelt analysis are presented and discussed.
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High-resolution and compact serpentine integrated grating spectrometer
Integrated astrophotonic spectrometers are integrated variants of conventional free-space spectrometers that offer significantly reduced size, weight, and cost and immunity to alignment errors, and can be readily integrated with other astrophotonic instruments such as nulling interferometers. Current integrated dispersive astrophotonic spectrometers are one-dimensional devices such as arrayed waveguide gratings or planar echelle gratings. These devices have been limited to resolving powers and spectral bins due to having limited total optical delay paths and 1D detector array pixel densities. In this paper, we propose and demonstrate a high-resolution and compact astrophotonic serpentine integrated grating (SIG) spectrometer design based on a 2D dispersive serpentine optical phased array. The SIG device combines a 5.2 cm long folded delay line with grating couplers to create a large optical delay path along two dimensions in a compact integrated device footprint. Analogous to free-space crossed-dispersion high-resolution spectrometers, the SIG spectrometer maps spectral content to a 2D wavelength-beam-steered folded-raster emission pattern focused onto a 2D detector array. We demonstrate a SIG spectrometer with resolving power and spectral bins, which are approximately an order of magnitude higher than previous integrated photonic designs that operate over a wide bandwidth, in a footprint. We measure a Rayleigh resolution of and an operational bandwidth from 1540 nm to 1650 nm. Finally, we discuss refinements of the SIG spectrometer that improve its resolution, bandwidth, and throughput. These results show that SIG spectrometer technology provides a path towards miniaturized, high-resolution spectrometers for applications in astronomy and beyond.
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- Award ID(s):
- 1817174
- PAR ID:
- 10250412
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Journal of the Optical Society of America B
- Volume:
- 38
- Issue:
- 7
- ISSN:
- 0740-3224; JOBPDE
- Format(s):
- Medium: X Size: Article No. A75
- Size(s):
- Article No. A75
- Sponsoring Org:
- National Science Foundation
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