One of the surprises of nonlinear optics, is that light may interact strongly with sound. Intense laser light literally “shakes” the glass in optical fibres, exciting acoustic waves (sound) in the fibre. Under the right conditions, it leads to a positive feedback loop between light and sound termed “Stimulated Brillouin Scattering,” or simply SBS. This nonlinear interaction can amplify or filter light waves with extreme precision in frequency which makes it uniquely suited to solve key problems in the fields of defence, biomedicine, wireless communications, spectroscopy and imaging. We have achieved the first demonstration of SBS in compact chip-scale structures, carefully designed so that the optical fields and the acoustic fields are simultaneously confined and guided. This new platform has opened a range of new functionalities that are being applied in communications and defence with breathtaking performance and compactness. My talk will introduce this new field and review our progress and achievements, including silicon based optical phononic processor.
In this paper, we present our recent results in the area of microwave photonics. Integrated microwave photonic bandpass
and bandstop filters were realized using stimulated Brillouin scattering (SBS). Our recent breakthrough in the fabrication
of chalcogenide waveguides has allowed us to achieve an on-chip SBS gain of >40 dB, enabling for the first time the
tailoring of the SBS response well beyond the intrinsic linewidth (~30 MHz). An electrical comb generated by an
arbitrary waveform generator was modulated onto an optical carrier to generate a broadened pump which via the SBS
effect created a flat and rectangular bandpass filter response in the RF domain. Controlling the number of pump lines
allowed bandwidth reconfigurability from 30 MHz to 440 MHz. The measured selectivity and the passband ripple were
>20 dB and <1.9 dB, respectively and the center frequency of the filter was tuned up to 30 GHz. A bandstop filter
response was realized by using a novel RF interferometry technique via accurate control of the amplitude and phase of
the sidebands of the modulated probe. The bandwidth was reconfigurable from 75 MHz-300 MHz and the central
frequency of the filter was tunable up to 30 GHz.
In this work, we discuss mode-locking results obtained with low-loss, ion-exchanged waveguide lasers. With Yb3+-doped phosphate glass waveguide lasers, a repetition rate of up to 15.2 GHz was achieved at a wavelength of 1047 nm with an average power of 27 mW and pulse duration of 811 fs. The gap between the waveguide and the SESAM introduced negative group velocity dispersion via the Gires Tournois Interferometer (GTI) effect which allowed the soliton mode-locking of the device. A novel quantum dot SESAM was used to mode-lock Er3+, Yb3+-doped phosphate glass waveguide lasers around 1500 nm. Picosecond pulses were achieved at a maximum repetition rate of 6.8 GHz and an average output power of 30 mW. The repetition rate was tuned by more than 1 MHz by varying the pump power.
In this work, we demonstrate 3-level laser operation in a Yb,Gd,Lu:KYW waveguide laser fabricated by combination of liquid phase epitaxy and Ar+ ion beam milling. Laser emission was observed at 981 nm with an absorbed threshold power of 23 mW and a slope efficiency of 58% without the use of any mirrors. With an HR/6%T cavity, the threshold was reduced to 13 mW. The output was single mode with beam radii of 4.8 μm and 3 μm in the in-plane and out-of-plane direction respectively. Laser emission was also observed at 999.8 nm with a threshold of 8 mW by using mirrors favouring the 999.8 nm transition and forming an HR/5%T cavity.
PbSe quantum dots (QDs) were grown in high-refractive-index low-melting-temperature leadphosphate glass. QDs with various sizes ranging from 2 nm to 5.3 nm were grown by controlling the growth parameters, heat-treatment temperature and time. The corresponding room-temperature exciton absorption was tuned within the infrared region from 0.93 μm to 2.75 μm. Photoluminescence was measured for samples with absorption peaks above 0.95eV. Real time quantum dot growth was demonstrated by monitoring the evolution of exciton absorption with temperature and time duration. As a demonstration of the use of QDs in laser applications, the saturation fluence (Fsat) of one of the QDs was evaluated and found to be ~2.1 μJ/cm2 at 1.2 μm.
Conference Committee Involvement (2)
Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications XII
19 August 2018 | San Diego, California, United States
Fiber Lasers and Glass Photonics: Materials through Applications