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Oeuvres du Cardinal P. Giraud, Archevêque de Cambrai : précédées de sa vie par M. l'abbé Capelle ; tome premier [-deuxième].
No full textEncabezamiento completado con: Enciclopedia universal ilustrada europeo-americana, t. XXVI, p. 176ColofónSignaturizadoAntepLa h. de grab. es litogr., retrato del autor: "Cabasson del., Lefort edit., E. Monnin, sc.
Broad tuning around degeneracy in a singly resonant synchronously pumped parametric oscillator by means of a diffraction grating: Errata
No full textErrata to article originally published here:Journal of the Optical Society of America B Vol. 16, Issue 9, pp. 1533-1538 (1999) •https://doi.org/10.1364/JOSAB.16.001533<br/
Use of a diffraction-grating in a synchronously-pumped parametric oscillator for broad tuning around degeneracy
No full textPeriodically poled lithium niobate (PPLN) has, in recent years, become a very useful and prominent material for use in optical parametric oscillators (OPO's) and other nonlinear optical devices. In synchronously pumped OPO's, the combination of high peak power from short pulse cw modelocked lasers and the large nonlinearity of PPLN, allows a very large parametric gain to be achieved. This, in turn, allows the use of convenient tuning elements, such as diffraction gratings, whose loss would be unacceptable for low gain cw devices. The strong frequency discrimination, of diffraction gratings, allows operation close to degeneracy, while still maintaining singly resonant operation (SRO). The attraction of operating around degeneracy is that due to the large parametric gain bandwidth, a broad tuning range can be conveniently achieved, without the need to change the temperature or the grating period of the PPLN. The standard approach for achieving singly resonant operation, by using resonator mirrors whose reflectivity discriminates against the idler wave, precludes reliable operation around degeneracy due to insufficient frequency discrimination. The diffraction grating in place of one of the mirrors overcomes this problem. In this paper we report on results obtained by equipping a PPLN OPO, pumped by a 4ps, 120MHz Nd:YLF laser at 1047nm, with a diffraction grating as one of its reflectors. A 20mm long PPLN crystal, with a grating period of 30.4 µm, held at a fixed temperature of 190 °C, was used to obtain a tuning range of 1900 - 2300nm, simply by tilting the diffraction grating. Fig. 1 shows this tuning behaviour. The good beam quality of the signal is confirmed by a measured M2 of 1.16. A measurement of the spectral width and pulse duration (via extra-cavity SHG auto-correlation) gives a time-bandwidth-product of 0.46
Broad tuning around degeneracy in a singly resonant synchronously pumped parametric oscillator by means of a diffraction grating
No full textThe use of a diffraction grating as a frequency-selective reflector, has allowed a synchronously pumped optical parametric oscillator based on periodically poled lithium niobate to tune over a wide range, 1900-2300 nm around degeneracy (2094 nm), on a single periodically poled lithium niobate grating at a fixed temperature. The grating ensures stable singly resonant operation over the whole of this range except for a very narrow range at degeneracy, where doubly resonant behavior is evident. The extent of this narrow range, ~6 nm, is confirmed by analysis
Compressed 200fsec pulses from a synchronously pumped optical parametric oscillator in periodically-poled lithium niobate
No full textA cw synchronously-pumped optical parametric oscillator (SPOPO) based on periodically-poled lithium niobate (PPLN) has produced a factor of 20 pulse compression, resulting in signal pulses as short as 200fs, when driven by 4ps pump pulses. Furthermore these compressed pulses extract most of the energy from the pump pulses so that the output signal pulses have higher peak power than the pump pulses. The principle of this pulse compression in a SPOPO has previously been demonstrated in BBO, using very intense (~1MW) Q-switched mode-locked pulse trains. The requirements for pulse compression were identified as high gain (10 quoted in ref. [1]) and large group-velocity walk-off between pump and resonated wave. Thus when the OPO resonator is biassed longer than the length for exact synchronism, the resonated signal pulse arrives at the nonlinear crystal late relative to the pump pulse and then 'walks-through' the pump pulse over the crystal length. The high gain allows the leading edge of the signal pulse to deplete the entire pump pulse so that essentially all of the pump pulse energy is extracted into the compressed pulse. We have shown that this principle can be extended to the case of cw mode-locking in PPLN, since high gains can be achieved for much lower pump powers. In fact we also find that the required gain in the cw mode locked case is only ~10. In the first experiment on a 1047nm pumped PPLN OPO, we used a 6mm sample that we had fabricated by electric-field poling. For these compression experiments we used a longer crystal (19mm, fabricated by Crystal Technology). The length was chosen to provide a group delay between pump and signal which was comparable to the 4ps pump pulse duration. A 4 mirror OPO resonator was used, either as a standing wave resonator or as a ring. The output mirror was an uncoated flat of LiNbO3 or ZnSe, providing a 15% reflectivity, hence forcing operation in the high-gain regime. The OPO was pumped by a diode-pumped Nd:YLF mode-locked laser (4psec, 120MHz, mean power 1W, Microlase DPM-1000-120). With the resonator set for exact synchronism, the signal pulses (tunable over 1.7-1.9µm) were 4psec in duration and the average power 300mW. With the resonator length increased by 50µm, compressed pulses of 200-250fsec were obtained at an average power of ~220mW. These compressed pulses were extremely stable, and had a time bandwidth product of ~0.33. The idler pulses, in the 2.3 to 2.7µm range, also showed compression, although to a smaller extent. These compression results confirm PPLN as a material well suited to ultrashort uses and offering a convenient route to broad tunability in the femtosecond regime
Stable singly resonant operation around degeneracy in a synchronously-pumped parametric oscillator by use of a diffraction-grating
No full textIn recent years periodically poled lithium niobate (PPLN) has become a very useful and prominent material for use in optical parametric oscillators (OPO's) and other nonlinear optical devices. The large nonlinearity of PPLN, combined with the high peak power available from short pulse cw modelocked lasers allows a very large parametric gain to be achievable in synchronously pumped OPO's. Close to degeneracy the gain bandwidth of these devices becomes very large and, theoretically, it is possible to tune the output wavelengths over a very wide range while maintaining a fixed temperature and domain grating period. However, when OPOs are operated close to degeneracy, there is a tendency to display doubly-resonant oscillation (DRO), with its well-known undesirable features of amplitude and frequency instability. We propose the use of a diffraction grating, as a frequency-selective reflector, to enable singly resonant operation over a wide range around degeneracy. In this paper we report on results obtained by equipping a PPLN OPO, pumped by a 4ps, 120 MHz Nd:YLF laser at 1047nm, with a diffraction grating as one of its reflectors, thus providing sufficient frequency discrimination to allow singly resonant operation very close to degeneracy. A diffraction-grating proves to be very well suited to tuning in a synchronously pumped OPO since the grating bandwidth appropriate to the spectral width of picosecond pulses is readily achieved and the grating losses are modest and easily accommodated by the high gain achievable from a synchronously pumped OPO using PPLN. Also, the broad gain bandwidth close to degeneracy offering an extensive tuning range, can be conveniently covered simply by rotating the grating. The range we have covered in this way is ftom 1900 to 2300nm (except for a very narrow range, ~6nm, around degeneracy). Fig.1 shows the signal tuning range achieved with a PPLN crystal of 30.4µm period, held at a temperature of 190°C. The pump depletion is also shown. The good beam quality of the signal is confirmed by a measured M2 of 1.16. A measurement of the spectral width and pulse duration (via extra-cavity SHG auto-correlation) gves a time-bandwidth-product of 0.46, close to the calculated value of 0.44 for a Gaussian pulse. This agile and simple tuning over a wide range (~700cm in our case) greatly enhances the practical utility of PPLN OPO's for a variety of spectroscopic applications. Fig. 1 Average output power (squares), and pump depletion (triangles) versus signal wavelength for a PPLN crystal of 30.4µm period, held at 190°C
A tunable femtosecond pulse source operating in the range 1.06-1.33 microns based on an Yb doped holey fiber amplifier
No full textWe report soliton pulse formation, amplification and soliton-self-frequency-shifting in an anomalously dispersive, Yb-doped holey fiber amplifier. Our fiber based system provides a highly-practical, continuously-tuneable, femtosecond pulse source operational in the important and difficult to access wavelength range from 1.05 to 1.35 microns
Generation of femtosecond pulses from order-of-magnitude pulse compression in a synchronously pumped optical parametric oscillator based on periodically poled lithium niobate
No full textWe demonstrate the generation of compressed. transform-limited 250-fs pulses, tunable in the near infrared, by means of synchronously pumped optical parametric oscillation in periodically poled lithium niobate. The almost 20-fold compression from the 4-ps pulse duration of the cw mode-locked Nd:YLF pump results in signal peak powers well in excess of the pump power
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