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1.
Appl Opt ; 61(4): 1068-1075, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-35201080

RESUMO

This paper presents a what we believe is a novel method to fabricate turnaround point long-period gratings (TAP-LPGs) possessing enhanced thermal stability and high sensitivity. It is shown by analysis and by experiment that LPG resonance in photosensitive fibers can be controlled partially by UV fluence and thermal annealing. TAP-LPGs with enhanced thermal stability were fabricated by following three steps: (I) finding grating period versus writing UV fluence for TAP operation; (II) writing gratings at a relatively higher period with higher fluence, in which case the resonance is out of phase; (III) controlled annealing so that the postannealed LPG operates at/near TAP. The thermal stability is enhanced. The average temperature sensitivity of dual peak resonance measured for a typical TAP-LPG in the temperature interval of 70°C-240°C is about 2.3 nm/°C. This study will be useful for the development of high temperature TAP-LPG sensors.

2.
Rev Sci Instrum ; 88(9): 093101, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28964210

RESUMO

Development of a demountable and see-through hollow cathode (HC) discharge lamp suitable for optogalvanic (OG) spectroscopy is described. The design of the HC lamp is simple, compact, and inexpensive. Lithium, investigated rarely by the OG method, is selected for cathode material as its isotopes are important for nuclear industry. The HC lamp is characterized electrically and optically for discharge oscillations free OG effect. Strong OG signals of lithium as well as neon (as buffer gas) are produced precisely upon copper vapor laser pumped tunable dye laser irradiation. The HC lamp is capable of generating a clean OG resonance spectrum in the available dye laser wavelength scanning range (627.5-676 nm) obtained with 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran dye. About 28 resonant OG lines are explicitly observed. Majority of them have been identified using j-l coupling scheme and assigned to the well-known neon transitions. One line that corresponds to wavelength near about 670.80 nm is assigned to lithium and resolved for its fine (2S1/2 → 2P1/2, 3/2) transitions. These OG transitions allow 0.33 cm-1 accuracy and can be used to supplement the OG transition data available from other sources to calibrate the wavelength of a scanning dye laser with precision at atomic levels.

3.
Appl Opt ; 56(6): 1579-1584, 2017 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-28234362

RESUMO

We report Doppler-free spectroscopy of neutral europium carried out using the saturation absorption technique. In the present experiment, Eu/Ne hollow cathode discharge is used as an atomic vapor source of europium. The Eu transition 4f76s2(S87/2°)→4f76s6p(P89/2) at 601.815 nm and 4f75d6s(aD1013/2°)→4f75d6p(zD811/2) at 580.027 nm are investigated. The frequency separation between the adjacent hyperfine transitions as well as hyperfine structure (HFS) constants are calculated from the obtained experimental spectra. The HFS constant obtained for the state 4f76s6p(P89/2) are A151=664.8 MHz; B151=293.5 MHz, and for state 4f75d6p(zD811/2), the values are A151=7.6 MHz; B151=-60 MHz. These obtained values are in good agreement with the results reported in the literature using laser induced atomic beam fluorescence technique.

4.
Rev Sci Instrum ; 86(11): 116107, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26628188

RESUMO

A novel circuit scheme is presented to improve timing jitter performance of high voltage pulse power supply utilizing semiconductor switches and magnetic pulse compressors, for pumping pulsed copper vapor lasers. The circuit effectively handles reflected energy from the laser load and achieves better jitter performance. The proposed circuit scheme had typical jitter value of ±2 ns whereas the standard circuit used earlier had jitter of more than ±10 ns under similar conditions. Performance of the circuit scheme is studied on a copper vapor laser operating at average laser power of 40 W.

5.
Appl Opt ; 54(11): 3106-14, 2015 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-25967293

RESUMO

This paper presents computational and experimental studies on wavelength/frequency fluctuation characteristics of a high pulse repetition rate (18 kHz) dye laser pumped by a frequency-doubled Nd:YAG laser (532 nm). The temperature gradient in the dye solution is found to be responsible for wavelength fluctuations of the dye laser at low flow rates (2800

6.
Appl Opt ; 54(4): 595-602, 2015 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-25967764

RESUMO

Laser-assisted Penning ionization (LAPI) is detected in a Ne/Eu hollow cathode (HC) discharge lamp using the pulsed optogalvanic (OG) method. In the Ne/Eu discharge, doubly ionized europium excited energy levels Eu[4f(7)(P(7/2,5/2)6)] lie within the thermal limit (∼kT) from the laser-excited neon's energy level [2p(5)(P3/202)3p or 2p(8) (in Paschen notation)] lying at 149,848 cm(-1). Therefore, Penning ionization (PI) of europium atoms likely to occur into its highly excited ionic states is investigated. To probe the PI of europium, the temporal profiles of its counterpart neon OG signal are studied as a function of discharge current for the transitions (1s(4)→2p(8)) and (1s(2)→2p(2)), corresponding to 650.65 and 659.89 nm wavelengths, respectively. It is observed that PI of europium alters the overall discharge characteristics significantly and, hence, modifies the temporal profile of the OG signals accordingly. The quasi-resonant ionizing energy transfer collisions between laser-excited Ne 2p(8) atoms and electronically excited europium P(9/2)10 atoms are used to explain the LAPI mechanism. Such LAPI studies carried out in HC discharge could be useful for the discharge of a metal-vapor laser with appropriate Penning mixtures.

7.
Appl Opt ; 53(19): 4320-6, 2014 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-25089996

RESUMO

The optogalvanic (OG) effect has been observed in a Eu/Ne hollow cathode discharge lamp using pulsed laser irradiation. An OG spectrum is recorded in dye laser wavelength region 574­602 nm using a boxcar-averager. In total 41 atomic lines are observed. Of these, 38 lines are assigned to neon transitions. Two lines observed corresponding to wavelengths 576.519 and 601.815 nm are assigned to europium transitions; (4f 7 6s 2 , S 8 7/2 →4f 7 6s6p , zP 6 7/2 ) and (4f 7 6s 2 , S 8 7/2 →4f 7 6s6p , zP 8 9/2 ), respectively, and the remaining line at 582.475 nm could not be assigned. The effect of the discharge current on europium as well as neon OG signals is also studied. At moderate discharge current values, an extra positive peak is observed in neon OG signal for the transition (1s 5 →2p 2 ) at 588.189 nm, which is explained by Penning-ionization process using the quasi-resonant energy transfer interactions between excited neon and europium atoms lying in 2p 2 and D 10 9/2 states, respectively.

8.
Opt Lett ; 15(8): 428-30, 1990 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-19767965

RESUMO

Copper-vapor lasers (CVL's) with positive-branch unstable resonators have been used extensively for reducing output-beam divergence. In contrast, the negative-branch unstable resonator has not been applied to CVL's. Here we study the performance of a negative-branch unstable-resonator CVL with various magnifications. A divergence of approximately 3.25 times the diffraction limit was obtained.

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