Broadband terahertz light source pumped by a 1 μm picosecond laser

We obtained a frequency tunable, low-coherence, picosecond, terahertz (THz) output with a high repetition rate from a picosecond Nd:YVO₄ bounce laser in combination with tandem periodically poled stoichiometric lithium tantalate and 4′-dimethylamino-N-methyl-4-stilbazolium tosylate crystals. The frequency of the THz output was tunable in the range 2.1–7.1 THz with a linewidth of ~3.5 THz at 2.2 THz. The THz output had a maximum peak power of ~180 mW and an average power of ~0.65 μW at 3.9 THz. This system has the potential to realize ultra-high speed, THz coherence tomography.     

Blue light generation in photonic crystal fibers with 1-μm femtosecond laser pulses

Using 300-fs 1039-nm Yb-doped fiber laser, we experimentally demonstrate blue light generation in a high-△ and high nonlinear photonic crystal fiber (PCF). The zero dispersion wavelength of PCF is 793 nm, detuning 245.8 nm from the pump wavelength. PCF allows a frequency conversion exceeding the octave of pump wavelength. The visible component of the measured output spectrum occurs in the fundamental mode and spans from 391.3 to 492.3 nm. The peak wavelength of 441.8 nm has a frequency detuning of 390 THz from the pump wavelength of 1039 nm.     

Fe:ZnSe laser pumped by a 2.93-μm Cr,Er:YAG laser

We demonstrated an Fe:ZnSe laser pumped by a 2.93-μm Cr, Er:YAG laser at liquid nitrogen and room temperature in single-shot free-running operation for the first time. The xenon flash lamp pumped Cr, Er:YAG laser had a maximum single pulse energy of 1.414 J, and the threshold and slope efficiency were 141.70 J and 0.70% which were respectively reduced by 29.3% and increased by 52.2% compared with the Er:YAG laser. At liquid nitrogen temperature of 77 K, the maximum single pulse energy of the Fe:ZnSe laser was 197.6 m J, corresponding to a slope efficiency of 13.4%. The central wavelength and full width at half maximum(FWHM) linewidth were 4037.4 nm and 122.0 nm, respectively. At room temperature, the laser generated a maximum single pulse energy of 3.5 mJ at the central wavelength of 4509.6 nm with an FWHM linewidth of 171.5 nm.     

Supercontinuum generation of highly nonlinear fibers pumped by 1.57-μm laser soliton

Highly nonlinear fibers(HNLFs) are crucial components for supercontinuum(SC) generation with laser solution.However, it is difficult to exactly estimate the structure of produced SC according to material parameters. To give a guideline for choosing and using HNLFs for erbium-fiber-based optical applications, we demonstrate SC generation in five types of HNLFs pumped by 1.57-μm laser solitons. All five fibers output a SC exceeding 1000 nm. Three different SC formation processes were observed in the experiment. By comparing optical parameters of these fibers, we find the zero dispersion wavelength(ZDW) of fiber has an important influence on the SC structure and energy distribution for a given pump source.     

Pulsed gas laser operating in the 0.193–10.6-μm range

Results are reported of an investigation of a system for exciting pulsed highpressure gas lasers. The method permits effective pumping of various active media, such as CO₂, excimer-molecules, N₂, etc. Lasing was obtained on seven different wavelengths in the range 0.193–10.6 m with pulse power more than 1 MW.Translated from Lazernye Sistemy, pp. 102–108, 1982.     

Angle-sensitive and fast photovoltage of silver nanocluster embeded ZnO thin films induced by 1.064-μm pulsed laser

Silver nanocluster embedded ZnO composite thin film was observed to have an angle-sensitive and fast photovoltaic effect in the angle range from –90o to 90o, its peak value and the polarity varied regularly with the angle of incidence of the 1.064-μ m pulsed Nd:YAG laser radiation onto the ZnO surface. Meanwhile, for each photovoltaic signal, its rising time reached ～2 ns with an open-circuit photovoltage of ～2 ns full width at half-maximum. This angle-sensitive fast photovoltaic effect is expected to put this composite film a candidate for angle-sensitive and fast photodetector.     

Light scattering and 2-μm laser performance of Tm:YAG ceramic

The scattering effect of Tm:YAG ceramic has been investigated and the scattering coefficient at 1064 nm wavelength is measured to be 0.014 cm⁻¹. Furthermore, a high power Tm:YAG ceramic laser with a slope efficiency of 10.7% has been built, which is end-pumped at a central wavelength of 805 nm. The 2-μm maximum output power is 7.1 W with an optical-optical conversion efficiency of 7.2%.     

Quadratic nonlinear response to 1.56-μm continuous wave laser in semi-insulating GaAs

The nonlinear photoresponse to a 1.56μm infrared continuous wave laser in semi-insulating （SI） galliu- marsenide （GaAs） is examined. The double-frequency absorption （DFA） is responsible for the nonlinear photoresponse based on the quadratic dependence of the photocurrent separately on the coupled optical power and bias voltage. The electric field-induced DFA remarkably affects the native DFA in SI GaAs. The surface electric field or the surface band-bending of SI GaAs significantly affects the magnitude variation of the Dhotocurrent and dark current     

Suppression of laser noise in CW 337μm HCN lasers

In a d.c.-discharge-excited 337 μm HCN laser, amplitude laser noise has been observed at the frequency range of 30 kHz to 1 MHz. The laser noise is classified into three types; oscillation noise having sharp peaks, broadly distributed noise having a center frequency and 1/f-noise. Characteristics of the laser noise have been studied experimentally. The laser noise is caused by small oscillation which appears on d.c.-discharge current and by random fluctuations of current and plasma density. The laser noise has been suppressed more than 30 dB by adjusting the laser parameters such as discharge current, pressure and flow rates of mixed gas (CH4₄ + N₂ + He) and added He.     

Efficient 2.7-μm emission in Er3＋-doped bismuth germanate glass pumped by 980-nm laser diode

An Er 3+-doped lead-free bismuth germanate glass is synthesized. Its 2.7-μm emission property is analyzed, and the efficient 2.7-μm emission from the glass is observed under 980-nm laser diode excitation. The prepared glass possesses high spontaneous transition probability (64.8 s 1 ) and a large calculated emission cross section (6.61×10 21 cm 2 ) corresponding to the 4I11/2→4I13/2 transition. The multiphonon relaxation rate for the excited state 4I11/2 is only 236 s 1 . Therefore, the excellent spectroscopic properties and outstanding thermal stability suggest that this glass is a suitable host for developing solid-state lasers operating in the mid-infrared.     

Nonlinear change in refractive index and transmission coefficient of silicon at long-pulse,mJ-range, 1.54-μm excitation

An experimental study and theoretical modeling of the nonlinear changes in transmission coefficient and refractive index of mono-crystalline Silicon (Si) at long-pulse, mJ-range, single-beam Z-scan probing at 1.54 μm wavelength are reported. It is shown experimentally that at increasing pulse energy density the photo-induced darkening permanently increases in Si while its photo refraction properties demonstrate a more complicate character, being a product of various type nonlinearities. A theoretical analysis based on simple assumptions of a square-shape pulse in the time domain and Gaussian spatial distribution of the probe beam allows fitting of a whole of the experimentally measured open- and closed-aperture Z-scans through an account of the main contributions in the light-induced absorption and refractive index nonlinearities. These are revealed to originate from non-direct two-photon absorption and Kerr effect, induced absorption and dispersion of light-generated free carriers, and light-induced thermal lensing.     

AlGaInAs multiple-quantum-well 1.2-μm semiconductor laser in-well pumped by an Yb-doped pulsed fiber amplifier

An AlGaInAs multiple quantum well structure is reported as an effective gain medium of the in-well pumped high-peak-power semiconductor disk laser at 1.2 μm. We use an Yb-doped pulsed fiber amplifier as the pump source to effectively optimize the output characteristics. The maximum average output power of 1.28 W and peak output power of 0.76 kW is obtained at 1225 nm lasing wavelength under 60 kHz pump repetition rate and 28 ns pump pulse width.     

Judd-Oflet analysis of spectrum and laser performance of Ho：YAP crystal end-pumped by 1.91μm Tm：YLF laser

The Ho:YAP crystal is grown by the Czochralski technique.The room temperature polarized absorption spectra of Ho:YAP crystal was measured on a c cut sample with 1 at% holmium.According to the obtained Judd-Ofelt intensity parameters Ω2 = 1.42 × 10-20 cm2,Ω4 = 2.92 × 10-20 cm2,and Ω6 = 1.71 × 10-20 cm2,this paper calculated the fluorescence lifetime to be 6 ms for 5I7 →5 I8 transition,and the integrated emission cross section to be 2.24×10-18 cm2.It investigates the room temperature Ho:YAP laser end pumped by a 1.91 μm Tm:YLF laser.The maximum output power was 4.1 W when the incident 1.91 μm pump power was 14.4 W.The slope efficiency is 40.8%,corresponding to an optical to optical conversion efficiency of 28.4%.The Ho:YAP output wavelength was centred at 2118 nm with full width at half maximum of about 0.8 nm.     

Diode laser measurements of line strengths and widths in the 4.5-μm bands of N2O

We have made line-strength measurements in the N₂O ν₃-fundamental region using a tunable diode-laser spectrometer. From these measurements and the Herman-Wallis factor determined by Boissy et al., we find the ν₃-fundamental band strength to be S_v = 1203 ± 22 cm⁻² atm⁻¹ at 297 K. Line-broadening parameters for two ν₃-fundamental lines were determined using nitrogen (N₂) as the broadening gas. Measured strengths and N₂ line-broadening parameters for several (ν¹₂ + ν₃ − ν¹₂) hot-band lines are also presented.     

X-ray spectra from laser produced highly ionized hafnium plasma in the 4.1–4.5 Å range

X-ray spectra of highly ionized hafnium atoms have been obtained from laser produced plasmas in the 4.1–4.5 Å range. Using quasi-relativistic configuration interaction calculations of the wavelengths and transition probabilities, the observed spectral band structure can be interpreted as being due to 3d–6f transitions of the NiI—GeI like ionization states of hafnium.     

Low-parasitic ESD protection strategy for RF ICs in 0.35μm CMOS process

A systemic and comprehensive ESD-induced parasitic model is presented in this paper, which is used to analyse the parasitic influences of electrostatic discharge (ESD) protection circuits on the performance of radio frequency applications. A novel low-parasitic ESD protection structure is made in a 0.35\mum 1P3M silicide CMOS process. The measured results show that this novel structure has a low parasitic capacitance about 310fF and a low leakage current about 12.2nA with a suitable ESD robustness target about 5kV human body model.     

2.1μm Ho：LuAG ceramic laser intracavity pumped by a diode-pumped Tm：YAG laser

We report a compact Ho：LuAG ceramic laser intracavity pumped by a diode-pumped Tm：YAG ceramic laser. The laser oscillation is accomplished by using a common linear cavity configuration containing Tm：YAG and Ho：LuAG ceramics. The 1.0 at.% Ho：LuAG ceramic laser yields 1.15 W of maximum output simultaneously at 2094 and 2100 nm with a beam quality factor of M2-2.8.     

High quality 2-μm GaSb-based optically pumped semiconductor disk laser grown by molecular beam epitaxy

The epitaxial growth conditions and performance of a diode-pumped GaSb-based optically pumped semiconductor disk laser(SDL) emitting near 2.0 μm in an external cavity configuration are reported. The high quality epitaxial structure,grown on Te-doped(001) oriented GaSb substrate by molecular beam epitaxy, consists of a distributed Bragg reflector(DBR), a multi-quantum-well gain region, and a window layer. An intra-cavity SiC heat spreader was attached to the gain chip for effective thermal management. A continuous-wave output power of over 1 W operating at 2.03 μm wavelength operating near room temperature was achieved using a 3% output coupler.     

Thermal Lensing, Laser Performance at 1.06 μm and 0.53 μm of a NYAB Laser End pumped by a Diode laser array

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