Eye-safe radiation source based on an optical parametric oscillator

Водчиц, А. И.; Дашкевич, В. И.; Казак, Н. С.; Pavlenko, Vitaly; Pokryshkin, V. I.; Petrovich, I. P.; Rukhovets, V. V.; Kraskovskii, A. S.; Orlovich, V. A.

doi:10.1007/s10812-006-0070-8

Cited by 6 publications

(6 citation statements)

References 15 publications

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“…The results of this work and [20] show that the beam divergence for an OPO with an unstable cavity is reduced with a decrease in the divergence of the pump radiation, as for the case of OPOs with other types of cavities [26]. Since for a number of practical applications of eye-safe radiation sources based on OPOs, we are interested in not only the angular characteristics but also the energy characteristics of the radiation, the most acceptable method for reducing the divergence of the fundamental radiation is to increase the length of the cavity in the pump laser.…”

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confidence: 64%

“…In this case, we focused our attention on both the temporal development of lasing and on the change in the spatial characteristics of the emission. To construct the pump laser, as in the previous paper [20] devoted to study of intracavity OPOs with multimode pumping, we used a potassium gadolinium tungstate crystal activated by neodymium ions: KGd(WO 4 ) 2 :Nd 3+ (KGW:Nd). Compared with other widely used laser media such as YAG:Nd 3+ , YLF:Nd 3+ , and YVO 4 :Nd 3+ [1][2][3][4][5][6][7][8][9][10][11][12][13], this laser material is characterized by a higher atomic concentration of the activator and relatively high lasing transition cross sections.…”

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confidence: 99%

“…Measurement of the spectral transparency of the crystal showed that its transmission at the wavelength of the idler wave (λ idler ≈ 3.33 µm) was no greater than 20%. Also considering that in the given spectral region, the reflection coefficients of the mirrors of the OPO cavity are no greater than 10%, we can say that the studied OPOs are single-cavity types and mainly enable generation of pulsed signal wave radiation (λ s = 1.578 µm [20]). The substrates of the mirrors M 3 and M 4 , forming the OPO cavity ( Fig.…”

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Comparative studies of eye-safe intracavity and extracavity optical parametric oscillators with an unstable telescopic cavity

et al. 2006

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We have experimentally studied the lasing characteristics of an eye-safe optical parametric oscillator (OPO) with an unstable telescopic cavity when it is placed inside (intracavity OPO) and outside (extracavity OPO) the plane-parallel cavity of a pulsed, nearly single-mode KGW:Nd pump laser. We used a KTP crystal as the nonlinear medium for the OPO. We have shown that the intracavity OPO has the higher lasing efficiency. We have observed that the distribution of nonlinear losses introduced by the intracavity OPO, nonuniform over the cavity cross section, leads to an increase in the diameter and divergence of the radiation beam from the pump laser and a dependence of its temporal lasing dynamics on the transverse beam coordinate. We propose a physical model qualitatively explaining the spatial and temporal lasing dynamics of a radiation source with an intracavity OPO. Both OPO versions generate beams of radiation with about the same divergence. When the KGW:Nd laser has an electrical pumping energy of 7.3 J and a cavity length of 77 cm, the intracavity OPO and the extracavity OPO emit pulses with energies of 14.5 mJ and 12.0 mJ and duration 18 nsec and 13 nsec respectively. The divergence of the eye-safe radiation (λ = 1.578 µm) at 86.5% of the total pulse energy is no greater than 5.5 mrad for an OPO output beam diameter of ≈2 mm. Introduction.A widely used approach to designing eye-safe pulsed radiation sources is based on optical parametric oscillation in KTP crystals, pumped by the emission from nanosecond neodymium lasers. Due to the good nonlinear optical properties of the KTP crystal, an optical parametric oscillator (OPO) based on such a crystal makes it possible to efficiently convert the wavelength of emission from neodymium lasers to the eye-safe range of the spectrum (1.54-1.61 µm), enabling generation of nanosecond pulses with energies from a few millijoules to hundreds of millijoules. Eye-safe radiation sources based on KTP crystals are made with the OPO positioned both outside [1][2][3][4][5] and inside [6-13] the pump laser cavity. As we know [14], the basic idea of an intracavity OPO involves using high radiation intensity in the "closed" cavity of the pump laser, which makes it possible to easily achieve the high OPO lasing thresholds (especially for an OPO designed for generation of signal or idler waves: a single-cavity OPO). The indicated advantage of the intracavity position is directly pertinent to eye-safe OPOs based on KTP crystals, since in practice they are usually made in the single-cavity version due to strong absorption of idler wave radiation in the KTP

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Comparative studies of eye-safe intracavity and extracavity optical parametric oscillators with an unstable telescopic cavity

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“…At present the feature analysis of extra-cavity OPO with LiNbO 3 resulted in a quantity of optical schemes [2][3][4][5][6][7]. The study of basic linear networks of OPO cavities [3,4] has shown that at satisfactory energy indictors the oscillator's divergence angle is rather high and runs up at the pumping energy increase.…”

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confidence: 99%

“…The implementation of OPO confocal unstable cavity [7,8] provides for high quality of output beam at a divergence angle that is close to a diffraction one. However, such cavities are extra sensitive to disalignment and are suitable only to provide oscillation at a stable wavelength.…”

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Extracavity Parametric Oscillation with Continuous and/or Discontinuous Frequency Tuning

Ayrapetyan¹,

Широкова²

2012

OPJ

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A continuously or/and discontinuously tunable LiNbO 3 Optical Parametric Oscillator (OPO) with the spectral range of 1.42 -4.24 um and shifting of 0…12 nm is created and investigated. The OPO resonator ring circuit provides for the radiation energy output value of up to 50 mJ. Radiation bandwidth narrowing of up to 0.7 cm -1 by introducing of the Fabry-Perot etalon into the OPO resonator has been obtained.

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Travelling-wave 1.57-µm optical parametric oscillator driven by a pulsed multimode Nd3+:YAG laser

et al. 2008

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The generation properties of an optical parametric oscillator (OPO) with a three-mirror ring resonator have been investigated under conditions of a pulsed pump by multimode radiation from a Nd 3+ :YAG laser. KTP crystals were used as the OPO nonlinear medium. At pump energies up to 100 mJ, decreasing the diameter d of the Nd 3+ :YAG laser beam causes a decrease in OPO radiation divergence and an increase in the generation efficiency at λ = 1.571 µm despite a decrease in the differential efficiency. At d = 2.25 mm and a KTP crystal total length of 40 mm, the efficiency of the pump conversion to the signal-wave pulse reaches 36.5%. Based on the traveling-wave OPO, a compact, highly effective, eye-safe laser source radiating pulses of up to 35 mJ in energy, 11 nsec in duration, and 10 Hz in repetition rate at electrical pump energy of ≤ 8 J is developed. At the 86.5% level of the total pulse energy, the source-beam divergence does not exceed seven diffraction limits.Introduction. One method for producing eye-safe (ES) radiation is based on the use of an optical parametric oscillator (OPO) of radiation in KTP (KTiPO 4 ) crystals pumped by radiation from Nd 3+ lasers (λ g ~ 1 µm). In view of the need to construct wholly solid-state sources, the use of OPO based on KTP crystals is an effective alternative to direct generation of ES radiation using Er-containing lasers [1, 2] and generation of ES radiation based on Raman transformation of Nd 3+ laser radiation operating at the 4 F 3/2 → 4 I 13/2 (λ g ~ 1.35 µm) transition [3][4][5]. Operation under non-critical phase synchronization and generation of ES radiation in the nanosecond range with energies of tenths and hundredths of millijoules can be achieved with pumping by Nd 3+ -radiation with amplitude modulation of an OPO in KTP crystals [6][7][8][9]. Owing to the high energy characteristics, these OPO are promising for many practical applications, several of which, however, require very reliable OPO operation and relatively low radiation divergence.One of the pathways for meeting these requirements is to construct an OPO based on an unstable telescopic resonator. The leakage of signal radiation from the axial region of the resonator to the periphery that is typical of such a resonator leads for several outputs of the resonator to a correlation of the phases for all points of the output cross section of the source and thereby reduces the divergence of the generated radiation. Furthermore, unstable resonators typically have a rather homogeneous distribution of the generation field in the transverse cross section. The advantages of the OPO with an unstable telescopic resonator have been demonstrated [10-13] for instances of extracavity and intracavity location of the OPO relative to the Nd 3+ -laser that generates both multimode pumping beams and beams for which the divergence is close to the diffraction limit.It has been shown [14] that the divergence of the radiation generated by an OPO under critical phase synchronism conditions can be decreased by combining effects o...

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Eye-safe radiation source based on an optical parametric oscillator

Cited by 6 publications

References 15 publications

Comparative studies of eye-safe intracavity and extracavity optical parametric oscillators with an unstable telescopic cavity

Comparative studies of eye-safe intracavity and extracavity optical parametric oscillators with an unstable telescopic cavity

Extracavity Parametric Oscillation with Continuous and/or Discontinuous Frequency Tuning

Travelling-wave 1.57-µm optical parametric oscillator driven by a pulsed multimode Nd3+:YAG laser

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