Quantitative optical coherence tomography for characterization of microscopic structures with varying refractive index

In this paper we have done back to back comparison of quantitive phase and refractive index from a microscopic image of waveguide previously obtained by Allsop et al. Paper also shows microscopic image of the first 3 waveguides from the sample. Tomlins et al. have demonstrated use of femtosecond fabricated artefacts as OCT calibration samples. Here we present the use of femtosecond waveguides, inscribed with optimized parameters, to test and calibrate the sensitivity of the OCT systems.

Demonstration of CoWDM using DPSK modulator array with injection-locked lasers

A practical implementation of coherent wavelength division multiplexing (CoWDM) is demonstrated for the first time using injection-locked lasers and a DPSK modulator array. For a 31.99 Gbit/s system (three subcarriers at 10.664 Gbit/s) the null-to-null spectral bandwidth was only 42.656 GHz and the average receiver sensitivity measured was -33.5 dBm when all subcarrier phases were optimised.

Formation and characterization of ultra-sensitive surface plasmon resonance sensor based upon a nano-scale corrugated multi-layered coated D-shaped optical fiber

We present experimental results on the performance of a series of coated, D-shaped optical fiber sensors that display high spectral sensitivities to external refractive index. Sensitivity to the chosen index regime and coupling of the fiber core mode to the surface plasmon resonance (SPR) is enhanced by using specific materials as part of a multi-layered coating. We present strong evidence that this effect is enhanced by post ultraviolet radiation of the lamellar coating that results in the formation of a nano-scale surface relief corrugation structure, which generates an index perturbation within the fiber core that in turn enhances the coupling. We have found reasonable agreement when we modeling the fiber device. It was found that the SPR devices operate in air with high coupling efficiency in excess of 40 dB with spectral sensitivities that outperform a typical long period grating, with one device yielding a wavelength spectral sensitivity of 12000 nm/RIU in the important aqueous index regime. The devices generate SPRs over a very large wavelength range, (visible to 2 mu m) by alternating the polarization state of the illuminating light.

Ultra-long raman laser with a feedback based on the Rayleigh scattering

This paper reports the Rayleigh scattering effects in ultra-long Raman fibre laser. It has been found that in a long fibre cavity (-100 km) the distributed feedback due to Rayleigh back scattering at propagation of light between fibre Bragg grating reflectors may be comparable with the lumped feedback provided by the FBG itself. As a result, Raman lasing in the fibre span limited by lumped (FBG) reflector at one side only appears possible due to significant reflection from the RS-based "random" distributed mirror at the other side. Thus, it concludes that a distributed Rayleigh scattering "random" mirror can form a cavity together with a single FBG spliced to the opposite cavity end.

Inscription of a 300-nm-period nanostructure in a pure fused silica

Very recently, using tightly-focused femtosecond near-IR pulses, periodical sub-micron structures have been recorded [1,2]. Such microfabrication utilizes the multi-photon approach, which allows the inscription inside various non-photosensitive optical materials. The combination of multi-photon excitation with the point-by-point technique offers the great potential of creating non-uniform chirped gratings by controlling the rate of femtosecond pulses or the sample translation speed.

Nonlinear diffraction in sub-critical femtosecond inscription

Material processing using high-intensity femtosecond (fs) laser pulses is a fast developing technology holding potential for direct writing of multi-dimensional optical structures in transparent media. In this work we re-examine nonlinear diffraction theory in context of fs laser processing of silica in sub-critical (input power less than the critical power of self-focusing) regime. We have applied well known theory, developed by Vlasov, Petrishev and Talanov, that gives analytical description of the evolution of a root-mean-square beam (not necessarily Gaussian) width RRMS(z) in medium with the Kerr nonlinearity.

42.6Gb/s RZ-ASK transmission over 2500km using quasi-lossless transmission spans

Here, for the first time, we experimentally demonstrate optical data transmission through such quasi-lossless fibre spans, which provide an entirely different nonlinear propagation regime to conventionally EDFA/Raman amplified systems. We demonstrate 42.6 Gb/s transmission over 2500 km of SMF-28 with an 82 km span length, and investigate the optimisation of the system in terms of launch power and nonlinear tolerance. Our results show the first ever data transmission experiment using an ultra-long Raman laser to provide quasi-lossless conditions in the transmission fibre. For a span length of 82 km we have shown 2500 km transmission over SMF-28 fibre at 42.6 Gb/s. Our quasi-lossless configuration had 6 dB lower optimum power and improved nonlinear tolerance compared with a conventional EDFA only system.

Low-loss waveguides in borosilicate glass fabricated by high-repetition-Rate femtosecond chirp-pulsed oscillator

We describe fabrication and characterisation of smooth low-loss waveguides in BK7 optical glass bymeans of direct femtosecond inscription with chirp-pulse oscillator, operating at 800 nm and 11 MHz repetition rate.

Characterization of nonlinear absorption in femtosecond laser inscription

Direct measurements of the absorbed energy in femtosecond laser inscription in a range of materials is performed. Key absorption parameters are characterized by fitting numerical modelling to measurements.

Novel optical chemsonsor based on etched D-fiber bragg gratings

A novel optical chemsensor concept based on the cladding etched Bragg gratings in D-fiber is demonstrated. Two etched devices have been used to measure the concentrations of sugar solution, giving sensitivity as high as 0.02nm/%.

3190-3275 nm tuneable, room temperature, external cavity InAs/AlSb Quantum Cascade Laser

We demonstrated a room temperature, tuneable, external cavity Quantum Cascade Laser for the use in compact spectroscopic gas sensing system. Wavelength tuning of 85 nm between 3190 nm and 3275 nm was achieved at room temperature.

Blue-to-red tunable SHG from a diode-pumped PPKTP waveguide

Summary form only given. Broadly tunable compact visible laser sources in the spectral region of 500-650 nm are valuable in biophotonics, photomedicine and for many applications including spectroscopy, laser projection and confocal microscopy. Unfortunately, commercially available lasers of this spectral range are in practice bulky and inconvenient in use. An attractive method for the realization of portable visible laser sources is the frequency-doubling of the infrared laser diodes in a nonlinear crystal containing a waveguide [1]. Nonlinear crystal waveguides that offer an order-of-magnitude increase in the IR-to-visible conversion efficiency also enable a very different approach to second-harmonic generation (SHG) tunability in periodically-poled crystals, promising order-of-magnitude increase of wavelength range for SHG conversion. This is possible by utilization of a significant difference in the effective refractive indices of the high-order and low-order modes in multimode waveguides [2]. The recent availability of low-cost, good quality semiconductor diode lasers, offering the coverage of a broad spectral range between 1 µ?? and 1.3 µp? [3,4], in combination with well-established techniques to fabricate good quality waveguides in nonlinear crystals, allows compact tunable CW laser sources in the visible spectral region to be realized [2].

High-power spectral bistability in a multi-section quantum-dot laser under continuous-wave or mode-locked operation

Wavelength bistability between 1245nm and 1295nm is demonstrated in a multi-section quantum-dot laser, controlled via the reverse bias on the saturable absorber. Continuous-wave or mode-locked regimes are achieved (output power up to 25mW and 17mW). © OSA/CLEO 2011.