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Photonic Ultra-Short Pulse Generators
Published in Le Nguyen Binh, Photonic Signal Processing, 2019
The optical spectrum of the tunable fiber ring laser over the tuning range of 15.5 nm is shown in Figure 7.56. The power of the pump LD is ~98 mW. The laser output is ~9 dBm. When scanning the resistance wire along the LCFBG over 50 mm, the lasing wavelength was shifted from 1546.8 to 1562.3 nm (or 15.5 nm range). It is observed that there is no spectral distortion of the lasing wavelength over the tuning range and that the output power is relatively constant with a power variation of <2 dB. The side-mode suppression ratio is greater than 30 dB. Figure 7.57 shows the output spectrum of the fiber ring laser and its stability with time. The time interval between the scans is 10 minutes. It can be seen that the laser output is very stable with time. The laser linewidth is measured using a scanning F-P interferometer with 10 GHz free spectral range and 50 MHz resolution. The measured linewidth is ~6.5 MHz, which is limited by the resolution of the scanning F-P interferometer.
Direct Modulation of Laser and Optical Injection Locking Sources
Published in Le Nguyen Binh, Optical Modulation, 2017
From the frequency noise or the phase noise spectrum, it is possible to evaluate the laser linewidth. It is common to specify a laser through its linewidth, although for very-high-spectral-purity sources this parameter cannot be measured directly and thus has a very limited practical interest. What is measured effectively is the frequency noise or the phase noise spectrum, and the linewidth evaluation requires a computation process from these data. Such a link between phase noise and power spectrum is a complex problem that has been the purpose of many papers [20,25–29], namely only a few. The only case that can be computed analytically is the one of white frequency noise [8], which leads to a Lorentzian line shape. However, for the type of laser concerned here, almost all the laser power is determined by the 1 = f part of the spectrum, and the Lorentzian formula is useless. The computation of the linewidth in the case of pure low frequency problem for an arbitrary phase noise spectrum with a combination of different slopes [27].
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Published in Arthur H. Hartog, An Introduction to Distributed Optical Fibre Sensors, 2017
The limitations on 6ɛand 6zdescribed so far are fundamental; however, they apply on the assumption that the signal-to-noise ratio is sufficient that contributions from receiver noise, for example, can be ignored. With coherent detection, this can be arranged in a wide range of circumstances. The laser linewidth must also be considered, and if it approaches the frequency-domain sample separation, it could further limit the measurand resolution.
Cryogenic buffer gas beams of AlF, CaF, MgF, YbF, Al, Ca, Yb and NO – a comparison
Published in Molecular Physics, 2022
Sidney C. Wright, Maximilian Doppelbauer, Simon Hofsäss, H. Christian Schewe, Boris Sartakov, Gerard Meijer, Stefan Truppe
We use two different continuous laser systems for this study. To detect Al, Ca, Yb, AlF, MgF and NO, we use a Ti:Sapphire laser (MSquared Solstis), whose output is frequency doubled in successive enhancement resonators containing a nonlinear optical crystal. The linewidth of the fundamental light is less than 400 kHz. A single stage of frequency doubling is sufficient to generate light near 360 nm (MgF) and 399 nm (Yb), and we use two successive doubling stages to generate UV light near 227 nm (AlF, NO, Al, Ca). The second laser system is a Coherent 899 ring dye laser (RDL) which generates light near 606 nm for the detection of CaF and near 552 nm for the detection of YbF. The laser linewidth is around 1 MHz. The laser frequencies are monitored with a HighFinesse WS8-10 wavemeter calibrated using a temperature-stabilised HeNe laser. Details on the absolute accuracy of the wavemeter can be found in reference [52] .1