Hostname: page-component-745bb68f8f-kw2vx Total loading time: 0 Render date: 2025-02-07T05:56:11.795Z Has data issue: false hasContentIssue false
  • English
  • Français

The development of a joule level of XeF(C-A) laser by optical pumping

Published online by Cambridge University Press:  05 December 2005

LI YU ,
JING-RU LIU ,
LIAN-YING MA ,
AI-PING YI ,
CHAO HUANG ,
XIAO-XIA AN ,
YONG-SHENG ZHANG ,
JIAN-CANG SU  and
ZHENG-ZHONG ZENG
LI YU
Affiliation:
Northwest Institute of Nuclear Technology, Xi'an, China
JING-RU LIU
Affiliation:
Northwest Institute of Nuclear Technology, Xi'an, China
LIAN-YING MA
Affiliation:
Northwest Institute of Nuclear Technology, Xi'an, China
AI-PING YI
Affiliation:
Northwest Institute of Nuclear Technology, Xi'an, China
CHAO HUANG
Affiliation:
Northwest Institute of Nuclear Technology, Xi'an, China
XIAO-XIA AN
Affiliation:
Northwest Institute of Nuclear Technology, Xi'an, China
YONG-SHENG ZHANG
Affiliation:
Northwest Institute of Nuclear Technology, Xi'an, China
JIAN-CANG SU
Affiliation:
Northwest Institute of Nuclear Technology, Xi'an, China
ZHENG-ZHONG ZENG
Affiliation:
Northwest Institute of Nuclear Technology, Xi'an, China
Rights & Permissions [Opens in a new window]

Abstract

A joule level of XeF(C-A) laser optically pumped by a sectioned surface discharge was developed. The irradiative intensity of pumping source was diagnosed by calculating XeF2 photo-dissociation wave evolvement which was photographed by a framing camera. The photon flux in the wavelength region of 140 to 170nm is about 5 × 1023 photon s−1cm−2, that corresponds to the irradiative brightness temperature of more than 25000 K. The laser experiments were carried out in different conditions. The maximum laser output energy of 2.5 J was obtained with the total conversion efficiency of 0.1%.

Keywords

Optical pumpingPhoto-dissociationXeF(C-A) laser
Type
Research Article
Information
Laser and Particle Beams , Volume 23 , Issue 4 , October 2005 , pp. 559 - 562
Copyright
© 2005 Cambridge University Press

1. INTRODUCTION

The femtosecond lasers was applied widely in many scientific fields (Limpouch et al., 2004; Gavrilov et al., 2004; Lan et al., 2004) during the last decade such as fast ions generation (Magunov et al., 2003), fabrication of debris-free microstructure, surface processing of materials (Lenzer et al., 1998; Bernardo et al., 2003), thin film deposition (Yao et al., 1999) and strong field physics etc.. For the high intensity femtosecond laser system, the chirped-pulse amplification (CPA) technology is usually used, which involves employment of complex and costly optics systems. A new method of direct amplification of femtosecond laser pulses in photo-chemically driven XeF(C-A) laser was developed (Mikheev, 1992; Malinovskii et al., 2001; Mikheev et al., 2004; Tcheremiskine et al., 2002).

XeF(C-A) laser has several attractive characteristics: (1) blue-green irradiative spectra region from 450 nm to 520 nm with the center wavelength of 480 nm, which coincidences with the second harmonic of the Ti: sapphire laser. (2) Higher saturation energy density of 50 mJ/cm2 compared with other excimer lasers. (3) Broad gain bandwidth (∼70 nm) which makes it possible to amplify ultrashort pulses down to 10 fs. With above properties, XeF(C-A) laser has perspective applications for ultrashort laser amplification and other fields.

Several kinds of optical pumping XeF(C-A) lasers was developed in different laboratories. Zuev et al. (1992) obtained XeF(C-A) lasers with output energy of 117 J by surface discharge pumping with the total stored energy of about 90 kJ. Mikheev et al. (1995) developed a photo-dissociation XeF(C-A) laser with the output energy of 14.5 J pumped by exploding wire excitation. Sentis et al. (1997) developed a XeF(C-A) laser pumped by formed-ferrite open discharge radiation, in which the output energy of 1.3J was obtained. Kaecht et al. (2003) developed a compact surface discharge system with the stored energy of 5k J for optical pumping, a single pulse energy >50 mJ from XeF(C-A) laser and >0.7 J of atomic iodine laser were obtained. The conversion efficiency with respect to the energy stored in the capacitors for most of the laser devices mentioned above were less than 0.1%, but the best efficiency of 0.17% up to now was obtained by Zuev et al. (1992).

We began the research work with XeF(C-A) laser in 1995 and several papers were published (Hu et al., 2001; Yu et al., 1998, 2001). We have been trying to develop the sectioned surface discharge pumping source because of the ability of its higher total conversion efficiency and the capability of repetitively operation. At present, the maximum output laser energy of 2.5 J with the total conversion efficiency of 0.1% was obtained. In this paper, the XeF(C-A) laser device and the experimental results are described in detail.

2. XeF(C-A) LASER DEVICE

The picture of XeF(C-A) laser is shown in Figure 1. The rectangular laser chamber is made of alnico with length of 116 cm and volume of about 10 liters. In order to decrease the intracavity losses, Brewster windows with aperture of 4.6 × 5 cm2 are used. Lasing is investigated by employing a stable resonator with the length of 152 cm. In the experiments, flat output mirrors with the output coupling of 4% and 8% in the spectral range of 450 to 510 nm are used, respectively. The reflectivity of spherical mirror of 5 m radius is better than 99.5%. In order to restrict the lasing on the B-X transition of XeF, the reflectivity of each mirror in 351 ± 5 nm is below 10%. Laser chamber could be evacuated to below 5 Pa. The initial concentration of XeF2 was determined by measuring the radiation absorption from a mercury lamp.

XeF(C-A) laser device.

A Teflon substrate is placed on a sidewall of the laser chamber as the discharge base of pumping source. The electrodes for the primary discharge are fixed on the surface of the Teflon. The schematic diagram of the pumping source is shown in Figure 2. The irradiation from a signal-channel sectioned surface discharge with the effective gain length of 80 cm is used to photolysis XeF2.The whole pumping source was divided by eight sections along the optical axis of the laser cavity. Each section consists of a pair of electrodes and one capacitor of 1 μF with the working voltage of 15 to 35 kV. The trigger electrode supplied high pulse of 25 kV is embedded in the Teflon substrate under main electrodes.

Schematic diagram of the pump.

3. THE DIAGNOSTICS OF PUMPING SOURCE PERFORMANCE

The discharge current in each section was measured by a Rogowski loop. The typical oscillogram of a current is shown in Figure 3 (waveform 1). In the case of the charging voltage of 25 kV, the peak value of the current is calculated to be about 32 kA and the rising rate of it is 2.9 × 109 A s−1. The equivalent inductance and resistance of the circuit are about 330 nH and 240 mΩ, respectively. The input average power per unit length of discharge plasma is 12 MW cm−1 during the first-half-cycle of the discharge and the deposited efficiency is 74%. The synchronization of the discharge of each section is very important for lasing. The jitter time of all discharge currents is measured to be smaller than 60 ns.

Discharge current and Laser waveforms.

The irradiative intensity of pumping source was diagnosed by calculating the time evolution of XeF2 photo-dissociation wave which was photographed by framing camera. Shown in Figure 4 are four frames of photolysis wave patterns recorded in the case of the initial XeF2 concentration of 1.57 × 1017 cm−3 and the charging voltage of 30 kV. The exposed time of each frame is 5 ns and apart of them are 160 ns. The interval between first frame and the beginning of the discharge current is 530 ns. The XeF2 photo-dissociation waves indicate the temporal and spatial change of the XeF(C-A) fluorescence layer. The velocity of the photolysis wave, as well as the thickness and the lifetime of fluorescence layer can be calculated from these patterns. We observed that the photo-dissociation wave with the thickness of 6 to 8 mm moved 3cm away from the Teflon surface in 2.2 μs.

Photographs of XeF2 photo-dissociation.

The results of calculation show that the velocity of the photo-dissociation wave decreases with time. The maximum speed exceeds 25 km s−1 at the beginning of the discharge and the average velocity exceeds 10 km s−1 during the first-half-cycle of the current. The effective lifetime of the excited layer is 700 ns under such a fast evolved of the photo-dissociation wave, which is shorter than 1.2 to 2 μs described in Zuev et al. (1992) and Sentis et al. (1997). The value of the XeF2 photo-dissociation rate W and the photon flux Φ into the absorption band (140 to 170 nm) of XeF2 can be determined by the following equations (Sentis et al., 1997; Zuev & Mikheev, 1991).

where N0 is the initial XeF2 concentration, τeff is the effective lifetime of an excited layer, R(t) is the radius of the photo-dissociation wave, r(t) is the discharge plasma radius and Vphd(t) is the velocity of the photo-dissociation wave. The photo-dissociation rate and the average irradiative intensity in the 140 to 170 nm spectra are 2.2 × 1023 actors s−1cm−3 and 5 × 1023 photon s−1cm−2, respectively, which correspond to the value of brightness temperature up to 25kK.

4. THE EXPERIMENTAL RESULTS

The laser experiments was carried out in the case of Ar:N2 = 3:2 at the total pressure of 100 kPa and XeF2 initial concentration ranging from 0.76 × 1017 to 1.4 × 1017cm−3. The laser output energy was measured with Jmax43 calorimeter. The laser pulse duration was detected by GD51Q photodiode and a typical laser pulse was shown in Figure 3 (waveform 2). A ULTIMA1024 camera with the speed of 2000 f/s was used to photograph the near-field laser beam pattern. The size of the laser beam is 2.7 cm × 3.6 cm. The spectrum of XeF(C-A) laser was recorded by a quartz spectrometer to be in the range of 470 to 495 nm.

The effect of the output coupling of laser cavity to the output energy was studied. The distance between the optical axis of laser and the surface of pumping source is 13 mm. The experimental results are shown in Figure 5. In the case of output coupling of 4%, the maximum output energy of 1.89 J with 700 ns pulse duration (FWHM) was extracted with a gas composition of XeF2:N2:Ar = 1.26 × 1017: 1.0 × 1019: 1.5 × 1019. The maximum output energy of 2.5 J was obtained with output coupling of 8% under the same composed gas and the total conversion efficiency is up to 0.1%. It is obvious that the output energies with transmissivity of 8% are higher than those in the case of 4% in the case of the initial XeF2 concentration from 0.76 × 1017 cm−3 to 1.4 × 1017 cm−3, which seems that the gain coefficient is higher than expected.

Output energy vs XeF concentration at different output coupling.

5. CONCLUSION

A joule level of XeF(C-A) laser optically pumped by a sectioned surface discharge was developed successfully. The rectangular laser chamber is made of alnico with length of 116 cm and volume of about 10 liters. The effective gain length of the laser is 80 cm and a plane-spherical stable resonator is used. The whole pumping source is divided by eight sections and each section consists of a pair of electrodes and one capacitor of 1 μF with the working voltage of 15 to 35 kV. The irradiative intensity of pumping source was diagnosed by calculating XeF2 photo-dissociation wave evolvement which was photographed by framing camera. The photon flux in the wavelength of 140 to 170 nm is about 5 × 1023 photon s−1cm−2, which corresponds to the irradiative brightness temperature of more than 25000 K.

The maximum output energy of 2.5 J was obtained with the output coupling of 8% and the gas composition of XeF2:N2:Ar = 1.26 × 1017: 1.0 × 1019: 1.5 × 1019. The maximum total conversion efficiency is up to 0.1%.

References

REFERENCES

Bernardo, A.D.I., Courtois, C., Cros, C., Matthieussent, G., Batani, D., Desai, T., Strati, F. & Lucchini, G. (2003). High-intensity ultrashort laser-induced ablation of stainless steel foil targets in the presence of ambient gas. Laser Part. Beams 21, 59–64.Google Scholar
Gavrilov, S.A., Golishnikov, D.M., Gordienko, V.M., Savel'ev, A.B. & Volkov, RV. (2004). Efficient hard X-ray source using femtosecond plasma at solid targets with a modified surface. Laser Part. Beams 22, 301–306.Google Scholar
Hu, Z.Y., Liu, J.R., Yu, L. & Zhang, Y.S. (2001). XeF(C-A) laser pumped by radiation from a segmented surface discharge. Acta Optica Sinica 21, 450–453.Google Scholar
Kaecht, B.A., Fraser, R.D., Wheeler, D.J., Zietkiewicz, C.J., Senin, A.A., Mikheev, L.D., Zuev, V.S. & Eden, J.G. (2003). Optical pumping of the XeF(C-A) and iodine 1.315 μm lasers by a compact surface discharge system. Opt. Eng. 42, 3612–3621.Google Scholar
Lenzer, M., Kruger, J., Sartania, S., Cheng, Z., Spielman, Ch., Mourou, G., Kautek, W. & Krausz, F. (1998). Femtosecond optical breakdown in dielectrics. Phys. Rev. Lett. 80, 4076–4079.Google Scholar
Lan, K., Fill, E. & Meyer-Ter-Vehn, J. (2004). Photo-pumping of XUV lasers by XFEL radiation. Laser Part. Beams 22, 261–266.Google Scholar
Limpouch, J., Klimo, O., Bina, V. & Kawata, S. (2004). Numerical studies on the ultrashort pulse K-alpha emission sources based on femtosecond laser-target interactions. Laser Part. Beams 22, 147–156.Google Scholar
Magunov, A.I., Faenov, A.Ya., Skobelev, I.Yu., Pikuz, T.A., Dobosz, S., Schmidt, M., Perdrix, M., Meynadier, P., Gobert, O., Mormand, D., Stenz, C., Bagnoud, V., Blasco, F., Roche, J.R., Salin, F. & Sharkov, B.Yu. (2003). X-ray spectra of fast ions generated from clusters by ultrashort laser pulses. Laser Part. Beams 21, 73–79.Google Scholar
Malinovskii, G.Ya., Mamaev, S.B., Mikheev, L.D., Moskalev, T.Yu., Sentis, M.L., Cheremiskin, V.I. & Yalovoi, V.I. (2001). Numerical simulation of the active medium and investigation of the pump source for the development of a photochemical XeF(C-A) amplifier of femtosecond optical pulses. Quan. Electr. 31, 617–622.Google Scholar
Mikheev, L.D. (1992). Possibility of amplification of a femtosecond pulse up to the energy 1 kJ. Laser Part. Beams 10, 473–478.Google Scholar
Mikheev, L., Levtchemko, K., Mamaev, S., Mislavskii, V., Moskalev, T., Sentis, M., Shirokikh, A., Tcheremiskine, V. & Yalovoi, V. (2004). Direct amplification of frequency doubled femtosecond pulse from Ti:Sa laser in photo-chemically driven XeF(C-A) active media. Proceedings of SPIE 5448, 384–392.Google Scholar
Mikheev, L.D., Stavrovskii, D.B. & Zuev, V.S. (1995). Photo-dissociation XeF laser operating in the visible and UV regions. J. Russian Laser Res. 16, 427–475.Google Scholar
Sentis, M.L., Tcheremiskin, V.I. & Delaporte, Ph.C. (1997). XeF(C-A) laser pumped by formed-ferrite open discharge radiation. Appl. Phys. Lett. 70, 1198–1200.Google Scholar
Tcheremiskine, V.I., Sentic, M.L. & Mikheev, L.D. (2002). Amplification of ultrashort laser pulses in the photolytically driven XeF(C-A) active medium. Appl. Phys. Lett. 81, 403–405.Google Scholar
Yao, D.S., Liu, J.R., Wang, L.G, Li, T.J., Yu, C.X. & Zhan, R.J. (1999). Deposition of diamond like carbon film by ultrashort pulsed excimer laser. ACTA Optica Sinica 19, 270–276.Google Scholar
Yu, L., Liu, J.R., Hu, Z.Y. & Huang, M.S. (1998). Experimental study on XeF(C-A) laser pumped by surface discharge radiation. Proceedings of the International Conference on Lasers'97, pp. 83–87. Soc. Opt. & Quantum Electron, Mclean, VA, USA.
Yu, L., Zhang, Y.S., Liu, J.R., Hu, Z.Y. & Yuan, X. (2001). Optically pumped Blue-green XeF(C-A) laser. Chinese Lasers 28, 205–208.Google Scholar
Zuev, V.S., Kashnikov, G.N. & Mamaev, S.B. (1992). XeF laser with optical pumping by surface discharge. Sov. J. Quan. Electr. 22, 973–979.Google Scholar
Zuev, V.S. & Mikheev, L.D. (1991). Photochemical Lasers. (Letokhov, V.S., Shank, C.V., Shen, Y.R. & Walther, H., Eds.). Switzerland: Harwood Academic Publishers.
Figure 0

XeF(C-A) laser device.

Figure 1

Schematic diagram of the pump.

Figure 2

Discharge current and Laser waveforms.

Figure 3

Photographs of XeF2 photo-dissociation.

Figure 4

Output energy vs XeF concentration at different output coupling.