Philippe C. Becker

Two-color synchronously mode-locked femtosecond Ti:sapphire laser

We report the simultaneous generation of two collinear synchronous mode-locked pulse trains, with central wavelength separations of 60 to 80 nm, from a single-cavity mode-locked Ti:sapphire laser. Near-transform-limited pulses of duration 50 to 70 fs were generated at each wavelength, with jitter of less than 20 fs between the two-color pulses. These pulses were directly used to generate infrared pulses centered at 9 μm, by difference-frequency mixing in an AgGaS2 crystal.

8-mV threshold Er/sup 3+/-doped planar waveguide amplifier

We report on the gain characteristics of a low threshold (8 mW) Er/sup 3+/-doped planar optical waveguide amplifier. Net fiber to fiber gain of 4.5 dB is achieved at a signal wavelength of 1536 nm with 80 mW of 980-nm pump power. This device represents significant progress toward a planar amplifier module pumped by a single laser diode.

High-repetition-rate femtosecond mid-infrared pulse generation.

Ultrashort mid-infrared pulses at a repetition rate of 82 MHz have been generated by difference-frequency mixing at the output of a single-cavity, two-color femtosecond Ti:sapphire laser. The center wavelengths of the midinfrared pulses are tunable from 7.5 to 12.5 microm. Their pulse durations range from 450 to 650 fs, as a function of the center wavelength.

Photoluminescence and electrical properties of erbium‐doped indium oxide films prepared by rf sputtering

Erbium‐doped indium oxide films were prepared by rf magnetron sputtering. The Er‐doped oxide films are conducting (or semiconducting) with a resistivity in the range of 10−3–103 Ωu2009cm, and are optically active, i.e., show a clear room‐temperature photoluminescence at 1.54 μm, corresponding to intratransitions in Er3+ ions. Compared with the undoped indium oxide films, the erbium doping was found to have the effect of increasing the resistivity (up to two orders of magnitude) of the films, mainly via a reduction of carrier concentration. Postdeposition annealing in air ambient significantly enhances both the Er3+ luminescence and Hall mobility (up to 60 cm2/Vu2009s), and reduces the carrier concentration. Postdeposition annealing in reducing ambient (N2/H2), however, decreases the resistivity dramatically, mainly via an increase of carrier concentration (up to 1020 cm−3), and also enhances the Er3+ luminescence.

Performance of a high concentration Er/sup 3+/-doped alumino silicate fiber amplifier

We report the gain, noise figure, output saturation power, and conversion efficiency of a highly concentrated Er/sup 3+/-doped alumino silicate fiber amplifier. We obtain a gain per unit length of 1.0 dB/cm, which corresponds to the highest gain per unit length obtained in an Er/sup 3+/-doped fiber amplifier. The pump power threshold ranges from 2 to 5 mW, depending on the fiber length.

Erbium Doped Semiconductor Thin Films Prepared by Rf Magnetron Sputtering

Highly Er-doped (∼ 10 20 atoms/cm 3 ) silicon and silica films were deposited by RF magnetron sputtering. Erbium was doped into the host material by co-sputtering technique. Deposited films (0.5 - 1.2 µm thick) were characterized by photoluminescence (PL), secondary ion mass spectroscopy (SIMS), and fluorescence decay measurements. Er-doped silica glass films show a strong, room-temperature luminescence at 1.54 µm wavelength. In contrast, Er-doped silicon films show a weak luminescence at room temperature. However, a big enhancement in the Er 3+ luminescence was observed after a proper annealing, for example, 900 °C for 30 to 120 min in air ambient, resulting in the luminescence intensities comparable with that of the Er-doped silica films. This enhancement is attributed to the oxygen incorporation into the Si host film during the annealing, thus forming an Er-doped oxide layer on top of the film. The result suggests that Er-O bonding plays important role in forming optically active erbium ions. Erdoped, three-component silicate glass (SiO 2 + A1 2 O 3 + MgO) films were also sputter deposited to investigate the dependence of Er 3+ luminescence on the host materials composition. Even stronger luminescence was observed from the Er-doped, three component silicate glass films compared with the Er-doped SiO 2 films.

Er-doped, epitaxial BaTiO/sub 3/ films deposited on MgO substrates for guided-wave optic devices

vances in nonlinear materials and engineering, the improvement of optical coating and the laser cavity design. Among them, the properties of laser host materials still determine the ultimate performance of a laser system. Current laser material research has progressed in three basic directions-high average power, low cost miniaturization and wavelength agility. For high average power lasers, Nd:YAG is still the material of choice due to its high thermal-mechanical strength. Slab geometry has become the favorable design for diode pumping and low thermal lensing. Current research is aimed at producing large size slabs via novel growth technique or sintering of polycrystalline ceramics. For low cost low power miniature laser systems, the host material selection is more flexible. Although Nd:YVO, has demonstrated excellent performances, the high cost and growth difficulty are two problems remained to be resolved. An alternative crystal, Nd:SFAP (Sr,(PO,)Z) has shown comparable performance and can be grown in large sizes at low cost. However, its market potential is closely linked to the cost of KTP nonlinear crystals since the intracavity doubling to both the green and the red are the major application of this crystal. One of the competing technology for the same application is the upconversion laser. So far only Er up-conversion green laser has shown adequate output from both single crystals and glass fibers. Both Tm and now Nd upconversions in ZBLAN fibres have demonstrated shorter wavelengths to the blue and UV. Current limits are cost and efficiency. In addition to fix wavelength lasers, there are also demands for tunable lasers operating from UV to far IR region. Obviously no single technology can provide such a broad tuning range with the same output or efficiency. Tunable lasers based on Cr and Ti3 are desirable because of the simplicity. However, tuning range is limited to 700 nm to 1 pm. Cr4 lasers in fosterite and YAG extend the tuning range from 1.1 to 1.5 pm. Recent discovery of Cr4:LiA10, and V4:LiGaOz provides peak emissions at 1.3 and 1.55 pm region and they may have specific applications in the telecommunication field. However, doping in these two compounds seems to require defect association which tends to degrade crystal quality. Another new laser based on C?:ZnS has shown tuning range from 2 to 3 km region. All of these are exciting development. Since there is no solid state tunable source in the UV and visible region, it needs nonlinear conversions using BBO or LBO to reach these wavelengths. Just recently a new nonlinear crystal, CLBO (CsLiB,O,,), has just discovered. The congruent melting nature of this crystal may promise low cost for these applications. Since there is no known tunable IR laser source beyond 3 pm, the only way to reach this region is to use OPO. At present, it has produced tuning just beyond 4 km. Clearly, finding any new laser hosts is getting harder but needs to continue. Short term solution may have to rely on laser engineering of known crystal hosts. Tu K2 1130

Er-doped silicate glass thin-film waveguide devices for integrated optics

tested, up to now. The measurement results and theoretical expectations are in good agreement. Future research will deal with the increase of the SH-efficiency by e.g., the use of channel-type waveguides, the use of more uniform Si[O]N layers deposited by an other LPCVD process, the use of multi-layer (2 or more Si[O]N films) structure and the use of an additional cladding layer on top of the Calix[4]arenes layer. 1. G. J. T. Heesink, et al., ”Novel calixarenes in thin films for efficient second harmonic generation,” Appl. Phys. Lett. 62(17), 2015-17 (1993). K. Worhoff, et al., “LPCVD SiON layers for application in SHG devices,” poster presentation, IOP Electro-Optics meeting, Veldhoven, The Netherlands, November 1994. I. J. Tebbutt: ”Effect of optical activity on type-I and type-I1 phase matching in second-harmonic generation,” Applied Optics 31(27), 581012 (1992). 4. R. Kashyap: “Phase-matched periodic electric-field-induced secondharmonic generation in optical fibers,” J. Opt. Soc. Am. B, 6(3), 31328 (1989). 2.

Er-doped silicate glass films prepared by co-sputtering for optical amplifiers

Er-doped glass thin films are drawing increasing attention for optical amplifiers suitable for integrated optic configuration. We have investigated deposition of highly Er-doped (mid 1019 atoms/cm3 silica films using Rf magnetron sputtering. Erbium was doped into the host material by cosputtering techniques. Deposited films (0.5 to 1.2-micrometers thick) were characterized by photoluminescence, secondary ion mass spectroscopy, and fluorescence decay measurements. We have also deposited Er-doped three component silicate glass (SiO2 + Al2O3 + MgO) films to investigate the dependence of Er3+ luminescence on the host materials composition. Optimum anneal temperature for the silicate glass films was found to be lower than that for the silica films while the Er3+ luminescence intensity was slightly higher for the silicate glass case.

Biwavelength operation of a short-pulse Ti:sapphire laser

Two collinear and synchronous modelocked pulse trains, with central wavelength separation adjustable between 55 and 90 nm, were obtained from a single cavity modelocked Ti:sapphire laser. Near transform limited pulses of duration 50 to 70 fs were generated at each wavelength, with very small jitter between the two color pulses.