scholarly journals Maser Amplifiers

1980 ◽  
Vol 87 ◽  
pp. 615-617
Author(s):  
E. Kollberg
Keyword(s):  
Low Noise ◽  
Stimulated Emission ◽  
Long Wavelength ◽  
Maser Amplifier ◽  
Amplification Process ◽  
Signal Field

When the lowest possible noise is required the maser amplifier remains the unquestionable amplifier choice for moderate bandwidth microwave and long wavelength millimeterwave receivers. The reason for the outstanding low noise properties of the maser is partly that it is cooled to a few degrees K (≲ 4 K) but also that the amplification process is the most fundamental one, i.e. amplification takes place when quanta (photons) are added directly to the signal field by stimulated emission of radiation from energetically excited particles.

Magnetooptical Studies and Stimulated Emission in Narrow Gap HgTe/CdHgTe Structures in the Very Long Wavelength Infrared Range

2018 ◽  
Vol 52 (4) ◽  
pp. 436-441
Author(s):  
V. V. Rumyantsev ◽  
L. S. Bovkun ◽  
A. M. Kadykov ◽  
M. A. Fadeev ◽  
A. A. Dubinov ◽  
...  
Keyword(s):  
Stimulated Emission ◽  
Infrared Range ◽  
Narrow Gap ◽  
Long Wavelength ◽  
Long Wavelength Infrared

scholarly journals A Review of the High-Power All-Solid-State Single-Frequency Continuous-Wave Laser

Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1426
Author(s):  
Weina Peng ◽  
Pixian Jin ◽  
Fengqin Li ◽  
Jing Su ◽  
Huadong Lu ◽  
...  
Keyword(s):  
Solid State ◽  
High Power ◽  
Continuous Wave ◽  
Beam Quality ◽  
Optical Loss ◽  
Low Noise ◽  
Stimulated Emission ◽  
Single Frequency ◽  
Laser Resonator ◽  
Laser Guidance

High-power all-solid-state single-frequency continuous-wave (CW) lasers have been applied in basic research such as atomic physics, precision measurement, radar and laser guidance, as well as defense and military fields owing to their intrinsic advantages of high beam quality, low noise, narrow linewidth, and high coherence. With the rapid developments of sciences and technologies, the traditional single-frequency lasers cannot meet the development needs of emerging science and technology such as quantum technology, quantum measurement and quantum optics. After long-term efforts and technical research, a novel theory and technology was proposed and developed for improving the whole performance of high-power all-solid-state single-frequency CW lasers, which was implemented by actively introducing a nonlinear optical loss and controlling the stimulated emission rate (SER) in the laser resonator. As a result, the output power, power and frequency stabilities, tuning range and intensity noise of the single-frequency lasers were effectively enhanced.

scholarly journals Magnetooptical studies and stimulated emission in narrow gap HgTe/CdHgTe structures in the very long wavelength infrared range

2018 ◽  
Vol 52 (4) ◽  
pp. 464
Author(s):  
V.V. Rumyantsev ◽  
L.S. Bovkun ◽  
A.M. Kadykov ◽  
M.A. Fadeev ◽  
A.A. Dubinov ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Optical Pumping ◽  
High Energy ◽  
Stimulated Emission ◽  
Infrared Range ◽  
Recombination Mechanism ◽  
Carrier Heating ◽  
Long Wavelength ◽  
Carrier Recombination ◽  
Long Wavelength Infrared

AbstractWe investigate the prospects of HgTe/HgCdTe quantum wells for long-wavelength interband lasers (λ = 15–30 μm). The properties of stimulated emission (SE) and magnetoabsorbtion data of QWs structures with wide-gap HgCdTe dielectric waveguide provide an insight on dominating non-radiative carrier recombination mechanism. It is shown that the carrier heating under intense optical pumping is the main factor limiting the SE wavelength and intensity, since the Auger recombination is greatly enhanced when carriers populate high energy states in the valence band.

Investigation of HgCdTe waveguide structures with quantum wells for long-wavelength stimulated emission

2017 ◽  
Vol 51 (12) ◽  
pp. 1557-1561 ◽  
Author(s):  
V. V. Rumyantsev ◽  
A. M. Kadykov ◽  
M. A. Fadeev ◽  
A. A. Dubinov ◽  
V. V. Utochkin ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Stimulated Emission ◽  
Long Wavelength

scholarly journals Optimization and selection of Galileo triple-frequency carrier linear combination

2021 ◽  
Vol 54 (1-2) ◽  
pp. 116-128
Author(s):  
Jun Wang ◽  
Xurong Dong ◽  
Wei Fu ◽  
Di Yan ◽  
Zengkai Shi
Keyword(s):  
Linear Combination ◽  
Low Noise ◽  
Integer Ambiguity ◽  
Convergence Time ◽  
Linear Combinations ◽  
Long Wavelength ◽  
Triple Frequency ◽  
Cycle Slip Detection ◽  
Wide Lane ◽  
Speed Up

The triple-frequency linear combination with a low noise, a long wavelength, and a weak ionosphere is beneficial to effectively eliminate or weaken the common errors, advance the reliability of cycle slip detection and repair, and speed up the convergence time of fixed ambiguity. By establishing the Galileo triple-frequency carrier linear combination model, three types of linear combinations are derived: Geometry-free (GF) combinations, minimum noise (MN) combinations, and ionosphere-free (IF) combinations. The geometric relationships of these linear combinations are displayed in the form of image. The results indicate that the angle formed by the IF combinations and the MN combinations is between 75.02° and 86.01°, which also illustrates that it is more difficult to meet the carrier phase combinations with a low noise and a weak ionosphere. Moreover, to guarantee the integer cycle characteristics of ambiguity, the combination coefficient must be an integer. Galileo triple-frequency linear combination is solved utilizing the extremum method. To sum up, the sum of the coefficients of the extra wide lane (EWL) combinations and wide lane (WL) combinations is zero, and the sum of the coefficients of the narrow lane (NL) combinations is one. (0, 1, −1) is the optimal triple-frequency linear combination in Galileo. Three independent linear combinations are selected separately from the EWL, WL, and NL to jointly solve the integer ambiguity. Further, it creates a prerequisite for high-precision and real-time kinematic positioning.

scholarly journals Low-Noise Mid-Infrared Photodetection in BP/h-BN/Graphene van der Waals Heterojunctions

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2532 ◽  
Author(s):  
Qin Lu ◽  
Li Yu ◽  
Yan Liu ◽  
Jincheng Zhang ◽  
Genquan Han ◽  
...  
Keyword(s):  
Dark Current ◽  
Flicker Noise ◽  
Van Der Waals ◽  
Low Noise ◽  
Current Fluctuations ◽  
Shallow Trap ◽  
Mid Infrared ◽  
Practical Applications ◽  
Long Wavelength ◽  
New Strategy

We present a low-noise photodetector based on van der Waals stacked black phosphorus (BP)/boron nitride (h-BN)/graphene tunneling junctions. h-BN acts as a tunneling barrier that significantly blocks dark current fluctuations induced by shallow trap centers in BP. The device provides a high photodetection performance at mid-infrared (mid-IR) wavelengths. While it was found that the photoresponsivity is similar to that in a BP photo-transistor, the noise equivalent power and thus the specific detectivity are nearly two orders of magnitude better. These exemplify an attractive platform for practical applications of long wavelength photodetection, as well as provide a new strategy for controlling flicker noise.

scholarly journals Femtosecond visible transient absorption spectroscopy of chlorophyll-f-containing photosystem II

2020 ◽  
Vol 117 (37) ◽  
pp. 23158-23164
Author(s):  
Noura Zamzam ◽  
Rafal Rakowski ◽  
Marius Kaucikas ◽  
Gabriel Dorlhiac ◽  
Sefania Viola ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Excited State ◽  
Photosystem Ii ◽  
Charge Separation ◽  
Transient Absorption ◽  
Spectral Feature ◽  
Cation Radical ◽  
Stimulated Emission ◽  
Transient Absorption Spectroscopy ◽  
Long Wavelength

The recently discovered, chlorophyll-f-containing, far-red photosystem II (FR-PSII) supports far-red light photosynthesis. Participation and kinetics of spectrally shifted far-red pigments are directly observable and separated from that of bulk chlorophyll-a. We present an ultrafast transient absorption study of FR-PSII, investigating energy transfer and charge separation processes. Results show a rapid subpicosecond energy transfer from chlorophyll-a to the long-wavelength chlorophylls-f/d. The data demonstrate the decay of an ∼720-nm negative feature on the picosecond-to-nanosecond timescales, coinciding with charge separation, secondary electron transfer, and stimulated emission decay. An ∼675-nm bleach attributed to the loss of chl-a absorption due to the formation of a cation radical, PD1+•, is only fully developed in the nanosecond spectra, indicating an unusually delayed formation. A major spectral feature on the nanosecond timescale at 725 nm is attributed to an electrochromic blue shift of a FR-chlorophyll among the reaction center pigments. These time-resolved observations provide direct experimental support for the model of Nürnberg et al. [D. J. Nürnberg et al., Science 360, 1210–1213 (2018)], in which the primary electron donor is a FR-chlorophyll and the secondary donor is chlorophyll-a (PD1 of the central chlorophyll pair). Efficient charge separation also occurs using selective excitation of long-wavelength chlorophylls-f/d, and the localization of the excited state on P720* points to a smaller (entropic) energy loss compared to conventional PSII, where the excited state is shared over all of the chlorin pigments. This has important repercussions on understanding the overall energetics of excitation energy transfer and charge separation reactions in FR-PSII.

Long-wavelength stimulated emission and carrier lifetimes in HgCdTe-based waveguide structures with quantum wells

2016 ◽  
Vol 50 (12) ◽  
pp. 1651-1656 ◽  
Author(s):  
V. V. Rumyantsev ◽  
M. A. Fadeev ◽  
S. V. Morozov ◽  
A. A. Dubinov ◽  
K. E. Kudryavtsev ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Stimulated Emission ◽  
Long Wavelength ◽  
Carrier Lifetimes
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