scholarly journals Gain-switched semiconductor laser driven soliton microcombs

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Wenle Weng ◽  
Aleksandra Kaszubowska-Anandarajah ◽  
Jijun He ◽  
Prajwal D. Lakshmijayasimha ◽  
Erwan Lucas ◽  
...  
Keyword(s):  
Semiconductor Lasers ◽  
Continuous Wave ◽  
Direct Detection ◽  
Critical Role ◽  
Optical Power ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Energy Conversion Efficiency ◽  
Microwave Range ◽  
Pulse Pump

AbstractDissipative Kerr soliton generation using self-injection-locked III-V lasers has enabled fully integrated hybrid microcombs that operate in turnkey mode and can access microwave repetition rates. Yet, continuous-wave-driven soliton microcombs exhibit low energy conversion efficiency and high optical power threshold, especially when the repetition frequencies are within the microwave range that is convenient for direct detection with off-the-shelf electronics. Here, by actively switching the bias current of injection-locked III-V semiconductor lasers with switching frequencies in the X-band and K-band microwave ranges, we pulse-pump both crystalline and integrated microresonators with picosecond laser pulses, generating soliton microcombs with stable repetition rates and lowering the required average pumping power by one order of magnitude to a record-setting level of a few milliwatts. In addition, we unveil the critical role of the phase profile of the pumping pulses, and implement phase engineering on the pulsed pumping scheme, which allows for the robust generation and the stable trapping of solitons on intracavity pulse pedestals. Our work leverages the advantages of the gain switching and the pulse pumping techniques, and establishes the merits of combining distinct compact comb platforms that enhance the potential of energy-efficient chipscale microcombs.

scholarly journals Мощные непрерывные лазеры InGaAs/AlGaAs (1070 нм) с расширенным латеральным волноводом мезаполосковой конструкции

2021 ◽  
Vol 55 (4) ◽  
pp. 344
Author(s):  
И.С. Шашкин ◽  
А.Ю. Лешко ◽  
В.В. Шамахов ◽  
Н.В. Воронкова ◽  
В.А. Капитонов ◽  
...  
Keyword(s):  
Semiconductor Lasers ◽  
Continuous Wave ◽  
Optical Power ◽  
Current Curve ◽  
Mesa Stripe

Semiconductor lasers with a 10 μm wide lateral waveguide of a mesa-stripe design were developed and their light characteristics were studied. Lasers with a 4.6mm long cavity is shown to have a continuous wave (CW) optical power of 2.6W at a heatsink temperature of 25◦C. Lasers with a shorter cavity (< 3mm) showed a lower value of the maximum optical power due to a thermal rollover of the light-current curve.

Tunable, continuous-wave Ti:sapphire channel waveguide lasers written by femtosecond and picosecond laser pulses

2012 ◽  
Vol 37 (22) ◽  
pp. 4630 ◽  
Author(s):  
Christos Grivas ◽  
Costantino Corbari ◽  
Gilberto Brambilla ◽  
Pavlos G. Lagoudakis
Keyword(s):  
Continuous Wave ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Channel Waveguide ◽  
Waveguide Lasers ◽  
Picosecond Laser Pulses

PICOSECOND OPTICAL LIMITING PERFORMANCE OF A NOVEL PPV-ZnPc CONJUGATED POLYMER

2000 ◽  
Vol 09 (03) ◽  
pp. 289-296 ◽  
Author(s):  
JINGJIN YU ◽  
LIMING WANG ◽  
QING WANG ◽  
MANKIT NG ◽  
LUPING YU
Keyword(s):  
Conjugated Polymers ◽  
Time Scale ◽  
Conjugated Polymer ◽  
Optical Power ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Picosecond Time Scale ◽  
Backbone Modification ◽  
Optical Power Limiting ◽  
532 Nm

A novel ZnPc monomer as well as PPV-ZnPc conjugated polymers have been synthesized and their optical power limiting (OPL) performances toward picosecond laser pulses at 532 nm have been measured. The comparison with the performance of C 60 under the same condition indicates that two of the compounds synthesized outperformed C 60 at picosecond time scale. It was found that conjugated PPV polymers containing a small amount of ZnPc cannot only preserve, but have also showed improvement over the monomer's OPL properties. It is believed that the backbone modification was responsible for the enhanced OPL performance.

scholarly journals Tunable and Passively Mode-Locking Nd0.01:Gd0.89La0.1NbO4 Picosecond Laser

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3179
Author(s):  
Shande Liu ◽  
Yuqing Zhao ◽  
Ke Zhang ◽  
Bo Chen ◽  
Ning Zhang ◽  
...  
Keyword(s):  
Output Power ◽  
Continuous Wave ◽  
Maximum Output Power ◽  
Picosecond Laser ◽  
Czochralski Method ◽  
Laser Pulses ◽  
Mode Locking ◽  
Maximum Output ◽  
Ultrafast Laser Pulses ◽  
First Time

A high-quality Nd0.01:Gd0.89La0.1NbO4 (Nd:GLNO) crystal is grown by the Czochralski method, demonstrating wide absorption and fluorescence spectra and advantage for producing ultrafast laser pulses. In this paper, the tunable and passively mode-locking Nd:GLNO lasers are characterized for the first time. The tuning coverage is 34.87 nm ranging from 1058.05 to 1092.92 nm with a maximum output power of 4.6 W at 1065.29 nm. A stable continuous-wave (CW) passively mode-locking Nd:GLNO laser is achieved at 1065.26 nm, delivering a pulse width of 9.1 ps and a maximum CW mode-locking output power of 0.27 W.

scholarly journals Theorical analysis of a monolithic all-active three-section semiconductor laser

2017 ◽  
Vol 9 (4) ◽  
pp. 131 ◽  
Author(s):  
Mohammed Mehdi Bouchene ◽  
Rachid Hamdi ◽  
Qin Zou
Keyword(s):  
Semiconductor Laser ◽  
Semiconductor Lasers ◽  
Continuous Wave ◽  
Laser Diodes ◽  
Optical Power ◽  
Longitudinal Mode ◽  
Distributed Feedback ◽  
Hole Burning ◽  
Spatial Hole Burning ◽  
Dfb Laser

We propose a novel semiconductor laser structure. It is composed of three cascaded active sections: a Fabry-Pérot laser section sandwiched between two gain-coupled distributed feedback (DFB) laser sections. We have modeled this multi-section structure. The simulation results show that compared with index- and gain-coupled DFB lasers, a significant reduction in the longitudinal spatial-hole burning can be obtained with the proposed device, and that this leads to a stable single longitudinal mode operation at relatively high optical power with a SMSR exceeding 56dB. Full Text: PDF ReferencesL.A. Coldren, "Monolithic tunable diode lasers", IEEE J. Select. Topics Quant. Electron. 6, 988 (2000) CrossRef O. Kjebon, R. Schatz, S. Lourdudoss, S. Nilsson, B. Stalnacke, L. Backbom, "30 GHz direct modulation bandwidth in detuned loaded InGaAsP DBR lasers at 1.55 [micro sign]m wavelength", Electron. Lett. 33(6), 488 (1997). CrossRef N. Kim, J. Shin, E. Sim, C.W. Lee, D.-S. Yee, M.Y. Jeon, Y. Jang, K.H. Park, "Monolithic dual-mode distributed feedback semiconductor laser for tunable continuous-wave terahertz generation", Opt. Expr. 17(16), 13851 (2009). CrossRef M.J. Wallace, R. ORreilly Meehan, R.R Enright, F. Bello, D. Mccloskey, B. Barabadi, E.N. Wang, J.F. Donegan, "Athermal operation of multi-section slotted tunable lasers", Opt. Expr. 25(13), 14426 (2017). CrossRef J.E. Carroll, J.E.A. Whiteaway, R.G.S. Plumb, "Distributed Feedback Semiconductor Lasers", Distributed feedback semiconductor lasers (IEE and SPIE, 1998). CrossRef H. Ghafour-Shiraz, Distributed Feedback Laser Diodes and Optical Tunable Filters (Wiley, 2003). CrossRef D.D. Marcenac, Ph.D dissertation (University of Cambridge, 1993). DirectLink L.M. Zhang, J.E. Carroll, C. Tsang, "Dynamic response of the gain-coupled DFB laser", IEEE J. Quant. Electr. 29, 1722 (1993). CrossRef W. Li, W.-P. Huang, X. Li, J. Hong, "Multiwavelength gain-coupled DFB laser cascade: design modeling and simulation", IEEE J. Quant. Electro. 36(10), 1110 (2000). CrossRef B.M. Mehdi, H. Rachid, in Proc. 3rd Intern. Conf. on Embedded Systems in Telecomm. and Instrument., Annaba, Algeria (2016). DirectLinkC. Henry, "Theory of the linewidth of semiconductor lasers", IEEE J.Quant. Electr. QE-18, 259 (1982). CrossRef K. Takaki, T. Kise, K. Maruyama, N. Yamanaka, M. Funabashi, A. Kasukawa, "Reduced linewidth re-broadening by suppressing longitudinal spatial hole burning in high-power 1.55-/spl mu/m continuous-wave distributed-feedback (CW-DFB) laser diodes", IEEE J. Quant. Electr. 39, 1060 (2003) CrossRef

Electric field probing by picosecond laser pulses

1992 ◽  
Vol 28 (12) ◽  
pp. 1137 ◽  
Author(s):  
A. Krotkus ◽  
V. Pašiškevičius
Keyword(s):  
Electric Field ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Picosecond Laser Pulses

scholarly journals An Efficient Radio Frequency Interference (RFI) Recognition and Characterization Using End-to-End Transfer Learning

2020 ◽  
Vol 10 (19) ◽  
pp. 6885
Author(s):  
Sahar Ujan ◽  
Neda Navidi ◽  
Rene Jr Landry
Keyword(s):  
Feature Extraction ◽  
Radio Frequency ◽  
Transfer Learning ◽  
Communication Networks ◽  
Continuous Wave ◽  
Critical Role ◽  
Video Stream ◽  
Radio Frequency Interference ◽  
Wave Interference ◽  
Continuous Wave Interference

Radio Frequency Interference (RFI) detection and characterization play a critical role in ensuring the security of all wireless communication networks. Advances in Machine Learning (ML) have led to the deployment of many robust techniques dealing with various types of RFI. To sidestep an unavoidable complicated feature extraction step in ML, we propose an efficient Deep Learning (DL)-based methodology using transfer learning to determine both the type of received signals and their modulation type. To this end, the scalogram of the received signals is used as the input of the pretrained convolutional neural networks (CNN), followed by a fully-connected classifier. This study considers a digital video stream as the signal of interest (SoI), transmitted in a real-time satellite-to-ground communication using DVB-S2 standards. To create the RFI dataset, the SoI is combined with three well-known jammers namely, continuous-wave interference (CWI), multi- continuous-wave interference (MCWI), and chirp interference (CI). This study investigated four well-known pretrained CNN architectures, namely, AlexNet, VGG-16, GoogleNet, and ResNet-18, for the feature extraction to recognize the visual RFI patterns directly from pixel images with minimal preprocessing. Moreover, the robustness of the proposed classifiers is evaluated by the data generated at different signal to noise ratios (SNR).

scholarly journals Laser-induced thermal grating spectroscopy based on femtosecond laser multi-photon absorption

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Maria Ruchkina ◽  
Dina Hot ◽  
Pengji Ding ◽  
Ali Hosseinnia ◽  
Per-Erik Bengtsson ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Laser Pulses ◽  
Photon Absorption ◽  
Gas Flows ◽  
Single Shot ◽  
Photon Excitation ◽  
Fs Laser ◽  
Thermal Grating ◽  
Grating Spectroscopy ◽  
First Time

AbstractLaser-induced grating spectroscopy (LIGS) is for the first time explored in a configuration based on the crossing of two focused femtosecond (fs) laser pulses (800-nm wavelength) and a focused continuous-wave (cw) laser beam (532-nm wavelength). A thermal grating was formed by multi-photon absorption of the fs-laser pulses by $$\hbox {N}_{{2}}$$ N 2 with a pulse energy around 700 $$\upmu $$ μ J ($$\sim $$ ∼ 45 TW/$$\hbox {cm}^{2}$$ cm 2 ). The feasibility of this LIGS configuration was investigated for thermometry in heated nitrogen gas flows. The temperature was varied from room temperature up to 750 K, producing strong single-shot LIGS signals. A model based on the solution of the linearized hydrodynamic equations was used to extract temperature information from single-shot experimental data, and the results show excellent agreement with the thermocouple measurements. Furthermore, the fluorescence produced by the fs-laser pulses was investigated. This study indicates an 8-photon absorption pathway for $$\hbox {N}_{{2}}$$ N 2 in order to reach the $$\hbox {B}^{3}\Pi _{g}$$ B 3 Π g state from the ground state, and 8 + 5 photon excitation to reach the $$\hbox {B}^{2}\Sigma _{u}^{+}$$ B 2 Σ u + state of the $$\hbox {N}_{2}^{+}$$ N 2 + ion. At pulse energies higher than 1 mJ, the LIGS signal was disturbed due to the generation of plasma. Additionally, measurements in argon gas and air were performed, where the LIGS signal for argon shows lower intensity compared to air and $$\hbox {N}_{{2}}$$ N 2 .

scholarly journals Enhancement of Photoacoustic Signal Strength with Continuous Wave Optical Pre-Illumination: A Non-Invasive Technique

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1190
Author(s):  
Anjali Thomas ◽  
Souradip Paul ◽  
Joy Mitra ◽  
Mayanglambam Suheshkumar Singh
Keyword(s):  
Methylene Blue ◽  
Continuous Wave ◽  
Optical Power ◽  
Signal Strength ◽  
Optical Beam ◽  
Clinical Translation ◽  
Optical Absorption Coefficient ◽  
Invasive Technique ◽  
Light Sources ◽  
Chicken Tissue

Use of portable and affordable pulse light sources (light emitting diodes (LED) and laser diodes) for tissue illumination offers an opportunity to accelerate the clinical translation of photoacoustic imaging (PAI) technology. However, imaging depth in this case is limited because of low output (optical) power of these light sources. In this work, we developed a noninvasive technique for enhancing strength (amplitude) of photoacoustic (PA) signal. This is a photothermal-based technique in which a continuous wave (CW) optical beam, in addition to short-pulse ~ nsec laser beam, is employed to irradiate and, thus, raise the temperature of sample material selectively over a pre-specified region of interest (we call the process as pre-illumination). The increase in temperature, in turn enhances the PA-signal strength. Experiments were conducted in methylene blue, which is one of the commonly used contrast agents in laboratory research studies, to validate change in temperature and subsequent enhancement of PA-signal strength for the following cases: (1) concentration or optical absorption coefficient of sample, (2) optical power of CW-optical beam, and (3) time duration of pre-illumination. A theoretical hypothesis, being validated by numerical simulation, is presented. To validate the proposed technique for clinical and/or pre-clinical applications (diagnosis and treatments of cancer, pressure ulcers, and minimally invasive procedures including vascular access and fetal surgery), experiments were conducted in tissue-mimicking Agar phantom and ex-vivo animal tissue (chicken breast). Results demonstrate that pre-illumination significantly enhances PA-signal strength (up to ~70% (methylene blue), ~48% (Agar phantom), and ~40% (chicken tissue)). The proposed technique addresses one of the primary challenges in the clinical translation of LED-based PAI systems (more specifically, to obtain a detectable PA-signal from deep-seated tissue targets).

scholarly journals Sputtering of Neutral Molecules and Molecular Ions From the Adenine Crystal Surface Induced by the UV Picosecond Laser Pulse

1982 ◽  
Vol 1 (1) ◽  
pp. 37-43 ◽  
Author(s):  
V. S. Antonov ◽  
V. S. Letokhov ◽  
Yu. A. Matveyets ◽  
A. N. Shibanov
Keyword(s):  
Laser Radiation ◽  
Kinetic Energy ◽  
Crystal Surface ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Molecular Ions ◽  
Laser Radiation Intensity ◽  
Ion Sputtering ◽  
Absorbed Energy ◽  
Picosecond Laser Pulse

This paper presents the results of observation of sputtering of neutral molecules and ions from the crystal adenine surface induced by fourth-harmonic Nd:YAG laser radiation with a pulse duration of 30 ps. The energy fluence of laser pulses was in the region (1–3) × 10−4 J/cm2. The kinetic energy distribution of the sputtered molecules spreads up to 0.7 eV. The experiment shows that the threshold of adenine molecular ion sputtering is connected with absorbed energy density in upper layers of the crystal surface but not by laser radiation intensity.

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