Tunable carbon monoxide overtone laser sideband system for precision spectroscopy from 2.6 to 4.1 microm

We report a source of tunable laser radiation for high-precision molecular spectroscopy in the 2.6- 4.1-microm spectral region. Laser light from a CO overtone laser is mixed with microwaves, generating tunable sidebands of ~1 mW of power. We achieve very high absolute frequency accuracy by frequency-offset locking the CO laser to a CO(2) laser secondary frequency standard. The uncertainty of the laser frequency is less than 30 kHz (Dnu/nu=3x10(-10)) , and the laser linewidth is of the order of 100 kHz. This tunable and ultrastable laser system is suitable for very accurate molecular spectroscopy and metrology in a most interesting wavelength region. We demonstrate an application of the system to saturated-absorption spectroscopy of a rovibrational transition of carbonyl sulfide.     

Tm-doped LiLuF4 crystal for efficient laser action in the wavelength range from 1.82 to 2.06 microm

Room-temperature continuous-wave laser action in a novel Tm-doped LiLuF(4) crystal emitting at around 1.9 microm is demonstrated. The crystal growth process, spectroscopic measurements, and laser performance are presented for different Tm concentrations. An overall tunability extending from 1817 to 2056 nm, a slope efficiency of 46%, and a maximum output power in excess of 1.1 W are reported.     

Picosecond laser complex for investigation of nonlinear transmittance of saturated absorbers

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 5, pp. 866–870, May, 1991.     

Continuous-wave 1.55 microm diode-pumped surface emitting semiconductor laser for broadband multiplex spectroscopy

A room-temperature-operating vertical external cavity surface emitting laser is applied around 1550 nm to intracavity laser absorption spectroscopy analyzed by time-resolved Fourier-transform interferometry. At an equivalent path length of 15 km, the high-resolution spectrum of the semiconductor disk laser emission covers 17 nm simultaneously. A noise-equivalent absorption coefficient at 1 s averaging equal to 1.5 x 10(-10) cm(-1)Hz(-1/2) per spectral element is reported for 65 km, the longest path length employed.     

10-W-level diode-pumped compact 2.78 microm ZBLAN fiber laser

We report on >9W transverse-fundamental-mode CW output near 3 mum from a 4m heavily erbium-doped ZBLAN double-clad fiber laser pumped by a collimated 100 W 975 nm laser diode array. The pump threshold of the fiber laser was about 1W, and the slope efficiency was 21.3%. The peak wavelength of free running was about 2708 nm at low pump power and moved to around 2785 nm at high pump power. Output of 9W was obtained when the launched pump power was 42.8W. The output, however, fluctuated intensively like a pulsed laser, and the operation broke down with optical damage of the pumping end facet when the pump was increased beyond 42.8 W. Therefore, alleviation of the operation fluctuation, heat management, and strengthening the pumping fiber are crucial considerations for the stable operation of 10-W-level mid-IR ZBLAN fiber lasers.     

皮秒级时间分辨超快高能脉冲激光光谱

介绍了一种利用光电摄谱法和条纹管相结合测量ps级时间分辨超快高能脉冲激光光谱的方法。论述了条纹相机工作原理和平面衍射光栅的分光原理,分析指出利用介绍的装置,可以实现波长300 nm ～1 600 nm、脉宽＞2 ps超快高能脉冲激光的光谱测量。采用1 054 nm超快高能脉冲激光器,实验得到了条纹像,对条纹像进行数据处理后得到测量光谱曲线,通过能量标定后,得到了超快高能脉冲激光器实际光谱曲线,验证了ps级时间分辨超快高能脉冲激光光谱方法。讨论了系统中耦合透镜组对光谱测量和光纤色散角对条纹图像的影响,论述了ps级时间分辨超快高能脉冲激光光谱的作用。随着条纹管制造技术的飞速发展,该方法可用于fs级激光光谱的测量。     

Design of a dye laser for nonlinear spectroscopy

Special requirements should be met by a pulsed dye laser in order to provide reproducible data in a nonlinear experiment. The cavity and pumping laser are chosen to minimize effects due to detailed dye characteristics. A suitable ruby pumping laser is described.     

Gravitational effects in nonlinear laser spectroscopy

The influence of a gravitational field on the shape of narrow nonlinear resonances in absorption spectra is investigated. It is shown that the action of the gravitational field on the velocity distribution of the excited particles may manifest itself as a gravitational drift. The possibility of gravitational broadening and shift of the non-linear spectral resonances is demonstrated.     

Picosecond pulse generation by intracavity nonlinear compression in self-injected Nd-YAG laser

A new type of laser which generates pulses with amplification band-limited picosecond duration is presented. 15 ps, 0.9 GW, 3 pps, λ = 1.06 μm in a single pulse are obtained with good stability. Accurate timing of the pulses can be achieved and no external pulse selection is required.     

AlGaInAs intracavity selective absorber for an efficient high-power Nd:YAG laser operation at 1.44 microm

We develop an AlGaInAs material as a promising intracavity selective absorber for an efficient high-power Nd:YAG laser at 1.44 microm. With the ISA to suppress operation at 1.06 microm, the output coupler at 1.44 microm can be straightforwardly designed and optimized. At a pump power of 16 W an output power of 2.5 W at 1.44 microm, with a slope efficiency of 23%, was achieved.     

Wavelength modulation spectroscopy with a widely tunable InP-based 2.3 microm vertical-cavity surface-emitting laser

We report on the successful application of recently developed 2.3 microm InP-based vertical-cavity surface-emitting lasers with a buried tunnel junction in a wavelength modulation spectroscopy measurement for carbon monoxide (CO) detection. The electrically pumped devices operate at room temperature under cw operation with stable single-mode emission and should allow for parts in 10(6) (ppm) level resolution measurement of CO with a standard optical setup.     

Picosecond fluorescence studies by intracavity gain spectroscopy in a modelocked dye laser

This article presents measurements which combine modelocking technique with intracavity spectroscopy. To test this approach, a sample (10^–5 m ethanolic solution of 1,4-dihydroxyanthranquinone) was inserted in a modelocked Ar⁺ ion laser and probed by intracavity pulses of a synchronously pumped dye laser. The probing of the sample results in an amplification of the dye laser output. Maximum output was measured if the pulses of the dye laser temporally overlapped with those of the Ar⁺ ion laser inside the sample. Under this condition, the spectral laser intensity was shaped by the spectrum of stimulated fluorescence which originated from a molecular vibronic state populated by pump laser excitation.Presented at LASERION '91, June 12–14, 1991, München (Germany)     

Picosecond spectroscopy of dye solutions

Using picosecond spectroscopy technique the rotational relaxation time of rhodamine 4C in solutions both in the ground and excited states is measured to be the same and equal to 250 ps.

While anti-Stokes exciting of non-substituted rhodamine ethanol solution by a single 530 nm picosecond pulse, the blue shift of the gain spectrum on 6 nm over 350 ps after excitation was observed, the process being explained by the orientational solvate relaxation.     

Picosecond spectroscopy of hydrogenated MBE-GaAs

Picosecond-resolved and steady-state photoluminescence at LHe temperature in low-energy ion-gun hydrogenated GaAs/GaAlAs heterostructures are reported. The exciton in the GaAs layer shows an increase in lifetime — up to a factor of 3 — for moderate hydrogenation, followed by a sharp decrease below the value for the untreated sample, for higher H doses. Luminescence efficiency shows a consistent behavior. Incorporation of H generates a strong D-A band falling 64 meV below the gap energy. The behavior for heavy hydrogenation indicates the formation of a new type of deep defect, not ascribed to surface damage, because of the protective GaAlAs layer, plus the fact that the excitonic emission of the latter shows no variation.     

1．3μm附近CO2的高灵敏度吸收光谱

采用可连续调谐半导体二极管激光器作为探测光源,将长程多通池吸收光谱、波长调制和谐波探测技术相结合,建立了一套具有高检测灵敏度和高分辨率的测量气态分子光谱及进行微量分析的研究装置.可以测量6.67×102Pa下～10-27 cm-1·(molecule·cm-2)-1的强度,最小可探测吸收达到～10-8.并利用该装置测量了CO2气体在1.31 μm附近的近红外吸收光谱,并用最小二乘法拟合实验数据获得了这一波段谱线的参数.同时测量的谱线参数与HITRAN数据库相比,发现15条数据库上没有报道的弱谱线.     

Two very efficient nonlinear laser absorption mechanisms in clusters

Experiments show strongly enhanced absorption of ultrashort superintense laser beams in clustered matter in the so-called collisionless regime. Despite numerous particle in cell simulations confirming this behavior, the underlying physical processes are not sufficiently clear. The familiar linear resonance absorption does not apply as long as the plasma frequency exceeds that of the laser. However, we show here that with increasing laser intensity the oscillations become nonlinear and can enter into resonance with the laser frequency because of restoring force lowering in Coulomb systems. Excellent absorption already at moderate intensities is the consequence. The other absorption mechanism we analyze explicitly consists in the coherent superposition of electron-ion collisions in ionized clusters. Collisional absorption enhancement factors of several orders of magnitude are found.     

Picosecond luminescence spectroscopy of highly excited GaAs

Time resolved luminescence of highly excited GaAs is studied using a streak camera. We observe the Mott transition from the electron-hole plasma to the excitonic state. This transition is smooth and does not show a phase separation. The plasmon sideband of the electron-hole plasma emission is identified.     

Picosecond infrared spectroscopy of molecules and semiconductors

Novel techniques for infrared spectroscopy on the picosecond time scale are presented. Ultrafast unimolecular reactions in organic molecules are studied by vibrational spectroscopy. The nonlinear infrared absorption of hot carriers in semiconductors is investigated.     

Frequency doubling of CO2 laser radiation at 10.6 microm in the highly nonlinear chalcopyrite LiGaTe2

Type-I phase matching for second-harmonic generation at 10.6 microm in LiGaTe(2) is demonstrated by using a tunable single-frequency continuous-wave CO(2) laser, and the nonlinear coefficient of LiGaTe(2) is determined from comparison with AgGaSe(2). The effective nonlinearity of LiGaTe(2) for this process amounts to 34.5 pm/V.