High-efficiency parametric converter based on KTP crystals

Naumov, V L; Onishchenko, A. M.; Podstavkin, A S; Шестаков, А. В.

doi:10.1070/qe2000v030n07abeh001780

Cited by 6 publications

(4 citation statements)

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“…An increasing divergence of the beam in the plane of the phase matching for greater pump beam intensities has been found also by other authors in similar configurations. [21][22][23] Being this phenomenon intrinsic to the mechanism of OPO generation in the required energy range (30-40 mJ), a possible solution is the use of a galilean telescope made of cylindrical lenses at the output of the OPO cavity when using large output energies. For the time being we limit the laser energy to values smaller than 20 mJ.…”

Section: The Beam Profilementioning

confidence: 99%

A laser system for the parametric amplification of electromagnetic fields in a microwave cavity

Agnesi

Braggio

Carugno

et al. 2011

Review of Scientific Instruments

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Section: The Beam Profilementioning

confidence: 99%

A laser system for the parametric amplification of electromagnetic fields in a microwave cavity

Agnesi

Braggio

Carugno

et al. 2011

Review of Scientific Instruments

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“…However, the divergence of the radiation from an OPO with a planar cavity is relatively large, since for short cavities it is determined more by the geometric aperture of the pumped volume than by the pump beam quality, if the pump beam divergence exceeds the diffraction limit [11]. A decrease in the divergence of the OPO radiation is facilitated by use of a ring cavity [10]. However, in order to achieve high radiation energy, this approach requires using several KTP crystals in the OPO, which increases the cost of the source.…”

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confidence: 98%

Eye-safe radiation source based on an optical parametric oscillator

et al. 2006

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We have studied an optical parametric oscillator (OPO) with an unstable telescopic cavity, placed inside the cavity of an actively Q-switched multimode Nd 3+ :KGW pump laser. We used a KTP crystal as the nonlinear medium for the OPO. We have compared the emission characteristics of OPOs with unstable telescopic and planar cavities. We have established that compared with the planar cavity, the unstable cavity reduces the OPO beam divergence and improves the spatial distribution of the radiation energy in the far wave zone.Based on our investigations, we have designed a compact eye-safe (λ = 1.578 µm) laser source with natural cooling, emitting (for electrical pumping energy 7.3 J) pulses with pulse energy 22 mJ and pulse duration 6 nsec. The FWHM beam divergence for the source is no greater than 3.5 mrad.Introduction. One of the most effective methods for generating eye-safe radiation is based on an optical parametric oscillator using crystals in the KTP family, pumped by radiation from Nd 3+ -containing lasers. KTP and KTA crystals have high radiation resistance, high nonlinear optical coefficients, and ensure lasing under noncritical phase matching conditions. Because of the indicated properties, they make it possible to rather efficiently, using single-cavity OPOs, to convert the wavelength of emission from Nd lasers to the wavelength range 1.54-1.61 µm. Single-cavity OPOs based on crystals of the KTP family are constructed using Nd:YAG, Nd:YLiF, and Nd:YVO 4 lasers with lamp and diode pumping [1][2][3][4].With pumping by Q-switched Nd lasers, OPOs based on KTP crystals can generate nanosecond pulses with energies of tens and hundreds of millijoules [5-10]. Such good power characteristics make KTP OPOs promising for many practical applications. However, the OPO beam divergence and field structure are no less important characteristics of eye-safe radiation (for example, for detection and ranging). Previously, high-power OPOs were generally constructed using linear planar cavities which, when the pump beam is matched with an eigenmode of the OPO cavity, ensure a sufficiently large waist (a few millimeters) and thus make it possible to operate below the damage threshold of the crystals. However, the divergence of the radiation from an OPO with a planar cavity is relatively large, since for short cavities it is determined more by the geometric aperture of the pumped volume than by the pump beam quality, if the pump beam divergence exceeds the diffraction limit [11]. A decrease in the divergence of the OPO radiation is facilitated by use of a ring cavity [10]. However, in order to achieve high radiation energy, this approach requires using several KTP crystals in the OPO, which increases the cost of the source.As shown by recent theoretical [12] and experimental [13,14] investigations, the divergence of the OPO radiation can be reduced by using an unstable telescopic cavity. The advantage of such a cavity over a planar cavity has been demonstrated for extracavity OPOs, pumped by laser beams with divergence close to...

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“…This mirror transformation of the beam cross section and the generation of the ring resonator in the travelingwave regime (which additionally increases the field homogeneity) were used to improve the characteristics of an OPO based on KTP crystals generating under non-critical phase synchronism conditions [15,16]. It was shown that low thresholds, high (up to ~40%) pumping transformation efficiency, and radiation divergence lower than that with a planar linear resonator can be achieved in an extracavity three-mirror ring OPO under both unimodal and multimodal pumping.…”

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confidence: 99%

“…However, it should be noted that these OPO characteristics were reached because of the placement in the cavity of three KTP crystals of total length 60 mm. Furthermore, the interrelationship of the pumping radiation parameters and the ES radiation was not investigated in detail [15,16].…”

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confidence: 99%

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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High-efficiency parametric converter based on KTP crystals

Cited by 6 publications

References 0 publications

A laser system for the parametric amplification of electromagnetic fields in a microwave cavity

A laser system for the parametric amplification of electromagnetic fields in a microwave cavity

Eye-safe radiation source based on an optical parametric oscillator

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

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