Pratheepan Madasamy

Waveguide distributed Bragg reflector laser arrays in erbium doped glass made by dry Ag film ion exchange

We demonstrate a distributed Bragg reflector (DBR) waveguide laser array by using an Ag film ion-exchange technique. We achieve an output power of 11 mW at 1540 nm for a coupled pump power of 145 mW, with a threshold of 60 mW and slope efficiency of 13%. The thin film ion exchange produces the highest index change possible at the surface, due to the ion exchange technique. Hence a wide array of wavelengths can be implemented in a single chip. We demonstrate a lasing wavelength range of 2.1 nm (1548.6 to 1550.7 nm) in an array with a single grating. Since the index change due to our process is large, we can fine tune the wavelengths of the array to fall on International Telecommunication Union (ITU) grid wavelengths by annealing. We demonstrate fine tuning of the wavelength for a channel from 1540.2 to 1540 nm, ITU specified wavelength, by annealing.

Buried ion-exchanged glass waveguides:burial-depth dependence on waveguide width

A detailed theoretical and experimental study of the depth dependence of buried ion-exchanged waveguides on waveguide width is reported. Modeling, which includes the effect of nonhomogeneous time-dependent electric field distribution, agrees well with our experiments showing that burial depth increases linearly with waveguide width. These results may be used in the proper design of integrated optical circuits that need waveguides of different widths at different sections, such as arrayed waveguide gratings.

Single-mode tapered waveguide laser in Er-doped glass with multimode-diode pumping

We report on a demonstration of a planar waveguide laser configuration for single-mode operation around 1550 nm using cost-effective multimode diode pumping. The laser was fabricated by Ag film ion exchange in a hybrid phosphate glass which has active and passive regions monolithically integrated in a single glass chip. Power of 54 mW at 1538 nm was measured from the single-mode output waveguide.

Dual-Grating Spectral Beam Combination of High-Power Fiber Lasers

We describe a dual-grating spectral beam combination (SBC) system to combine multiple high-power fiber laser outputs while maintaining near-diffraction-limited beam quality. The two gratings are parallel in a grating rhomb configuration, with input and output beams that are parallel but shifted with wavelength, rather than the typical angular dispersion of a single grating. The resulting advantage of the dual-grating SBC over other beam combination systems is the relaxation of the linewidth requirement. We combined two fiber lasers with output powers of 115 W each and linewidths of about 0.15 nm ( ~40 GHz) to produce a combined beam of 190 W power with near-diffraction-limited beam quality (M 2 ~ 1.18).

Poling of soda-lime glass for hybrid glass/polymer electro-optic modulators

We report on a poling process of soda-lime glasses that reduces their surface conductivity by five orders of magnitude. We show that this process enables the in-plane poling of high Tg (180 °C) electro-optic (EO) polymers coated on ion-exchanged channel waveguides fabricated in soda-lime glasses for hybrid modulators.

Fiber amplifier performance in γ-radiation environment

Fiber based amplifiers are being considered for use on low earth orbiting (LEO) satellites for next generation communication systems. This paper deals with evaluation of the performance of an Er/Yb based fiber amplifier in γ-radiation environment.

Comparison of spectral beam combining approaches for high power fiber laser systems

Spectral Beam Combination (SBC) of multiple fiber laser outputs has been shown to be an effective way to scale the power of fiber laser systems while maintaining near-diffraction-limited beam quality. The fiber SBC system maintains many of the key advantages of individual fiber lasers, such as high efficiency, excellent beam quality independent of output power and relaxed thermal management requirements. Several approaches to spectral beam combination have been demonstrated including single grating in linear oscillator, single grating in master oscillator power amplifier (MOPA), dual grating MOPA and dual grating ring oscillator configurations. Each of these variations has certain advantages in terms of the system design and fiber laser requirements. In this paper we analyze the different approaches and compare them in terms of combined beam quality, line-width requirements of the individual fiber laser channels, power scalability and system complexity. The results obtained using the different SBC approaches at Aculight are summarized in the context of this analysis.

Buried ion-exchanged glass waveguides featuring low birefringence with a broad range of waveguide widths

Optical communications networks require integrated photonic components with negligible polarization dependence, which typically means that the waveguides must feature very low birefringence. Recent studies have shown that waveguides with low birefringence can be obtained, e.g., by using silica on Si waveguides and by buried ion-exchanged glass waveguides. However, many integrated photonic circuits consist of waveguides with varying widths. Therefore, low birefringence is consequently required for waveguides having different widths. This is a difficult task for most waveguide fabrication technologies. In this paper we present theoretical and experimental results on waveguide birefringence for buried silver ion-exchanged glass waveguides. We show that the waveguide birefringence is on the order of 10-6 for waveguide mask opening widths ranging from 2 to 9 μm. The measured values are in good agreement with the values calculated with our modeling software for ion-exchanged glass waveguides. This unique feature of ion-exchanged waveguides may be of significant importance in a wide variety of integrated photonic circuits requiring polarization independent operation.

Single mode tapered waveguide laser in Er- doped glass with multimode-diode pumping

We propose a novel planar waveguide laser configuration for single mode operation around 1550 nm using cost-effective multimode diode pumping. We demonstrate the laser using Ag film ion exchange in a hybrid phosphate glass.

70-Watt green laser with near diffraction-limited beam quality

A 70-Watt green laser with M2<1.4 has been demonstrated. This green laser consists of an all-fiber-based IR pump laser at 1064 nm and a frequency-conversion module in a compact and flexible configuration. The IR laser produces up to 150 Watts in a polarized diffraction-limited output beam with high spectral brightness for frequency conversion. The IR laser is operating under QCW mode, e.g. 10 MHz with 3~5 ns pulse width or 700 MHz with 50 ps pulse width, to generate sufficient peak power for frequency doubling in the converter module. The IR laser and conversion module are connected via a 5-mm stainless-steel protected delivery fiber for optical beam delivery and an electrical cable harness for electrical power delivery and system control. Both the IR laser and converter module are run through embedded software that controls laser operations such as warm up and shut down. System overview and full characterization results will be presented. Such a high power green laser with near diffraction-limited output in a compact configuration will enable various scientific as well as industrial applications.