Room-temperature continuous-wave operation of Ti:sapphire buried channel-waveguide lasers fabricated via proton implantation

Abstract

Fabrication and laser operation of proton-implanted Ti:sapphire buried channel waveguides is reported for the first time to our knowledge. Without any postimplantation annealing of the structures, continuous laser operation near 780 nm was demonstrated at room temperature at an absorbed pump power threshold of 230 mW. Single-transverse-mode laser emission was observed with measured beam propagation factors M x 2 and M y 2 of 1.5 and 1.2, respectively. An output power of 12.4 mW for 1 W pump power was obtained with an output coupler of 4.6% transmission at the signal wavelength. Higher output powers were measured in waveguides with larger cross sections exhibiting multimode laser emission. © 2006 Optical Society of America OCIS codes: 130.3120, 230.7380, 140.3590, 140.3570, 230.7370, 350.3850. Proton implantation has recently attracted interest for fabrication of waveguide lasers, because protons, compared to higher-mass ions, allow for larger penetration depths and, therefore, can lead to deeper damage profiles. They also create less damage in the guiding region, which extends the prospects of developing waveguide devices. 1,2 This method has recently been proved capable of producing low-loss ͑ϳ0.7 dB/ cm͒ buried channel waveguides in undoped sapphire crystals without any postimplantation annealing.2 Ti:sapphire is a widely used laser system with broad tunability ͑650-1100 nm͒, which makes it suitable for the development of short pulse and broadly tunable lasers, 3 with potential applications in areas as diverse as biomedical imaging, spectroscopy, sensing, and microscopy. Due to its low peak emission cross section and the short fluorescence lifetime, Ti:sapphire lasers require high pump-power densities to achieve efficient cw lasing. Development of miniature Ti:sapphire channel waveguide lasers would offer the possibility to achieve low laser thresholds as a result of the confinement of the laser and pump modes. Such lasers have been realized in planar waveguide geometry via pulsed laser deposition (PLD), 4 and in channel waveguide geometry via thermal diffusion of Ti 2 O 3 into sapphire, 5 and a combination of PLD and photolithography-Ar + -beam milling, 6 respectively. However, the indiffused channel waveguides showed low slope efficiencies, typically of the order of ϳ0.1%, 5 while those produced by the latter method exhibited relatively high propagation losses ͑ϳ1.8 dB/ cm͒. These losses can be an unavoidable consequence of the PLD process itself and may, therefore, limit the prospects for future device developments.Here, we report, for the first time to our knowledge, the laser operation of Ti:sapphire buried channel waveguides fabricated by proton implantation. To date, lasing action in proton-implanted crystalline waveguides has been demonstrated in garnet-based (Nd:YAG) planar structures with guidance in one direction only. 1,7 Implantations were performed with high-energy protons ͑0.5-1 MeV͒ resulting in negative refractive index changes of the order of −0.5 to −1% for a 1 MeV proton beam and doses...

Optically pumped planar waveguide lasers, Part I: Fundamentals and fabrication techniques

“…To eliminate these defects the waveguides are subjected to high-temperature post-fabrication annealing, which however is undesirable in cases when their integration along with other functional components produced on the same chip in earlier fabrication steps is intended. Buried slab and channel waveguides exhibiting relatively low propagation loss (0.7 and 1 dB·cm -1 for the slab and channel structures, respectively) have been nevertheless produced without thermal annealing in undoped sapphire [332,333] and Ti:sapphire crystals [333,334]. [337] slab waveguide lasers.…”

Optical Waveguides Fabricated by Ion Implantation/Irradiation: A Review Optical Waveguides Fabricated by Ion Implantation/Irradiation: A Review

“…Unfortunately, their application as a tunable integrated light source is somewhat limited by its high loss (~10 dB/cm). This limitation is not present in the buried Ti:sapphire channel waveguides produced by proton implantation (Grivas et al, 2006;, whose very low loss (~1dB/cm) makes them a better choice. In this case laser operation (~780 nm) was achieved at room temperature, with an absorbed pump power threshold of 230 mW; the maximum output power and the slope efficiency were 17 mW and 3%, respectively.…”

Sapphire and other dielectric waveguide devices

“…Buried channel waveguides were produced by proton implantation in sapphire [5] and Ti:sapphire bulk crystals [6]. Proton irradiation in sapphire or Ti:sapphire results in a negative refractive-index change of the implanted zone.…”

“…A better lateral confinement is achieved by a vertically uniform distribution of the refractive-index change within the side barriers. Therefore, irradiations with several angles of incidence were performed, resulting in vertically stacked low-refractive-index barriers [6].…”