Nonlinear silicon photonics

Session - Silicon Photonics and Photonic Integrated Circuits IIAn intriguing optical property of silicon is that it exhibits a large third-order optical nonlinearity, with orders-ofmagnitude larger than that of silica glass in the telecommunication band. This allows efficient nonlinear optical interaction at relatively low power levels in a small footprint. Indeed, we have witnessed a stunning progress in harnessing the Raman and Kerr effects in silicon as the mechanisms for enabling chip-scale optical amplification, lasing, and wavelength conversion - functions that until recently were perceived to be beyond the reach of silicon. With all the continuous efforts developing novel techniques, nonlinear silicon photonics is expected to be able to reach even beyond the prior achievements. Instead of providing a comprehensive overview of this field, this manuscript highlights a number of new branches of nonlinear silicon photonics, which have not been fully recognized in the past. In particular, they are two-photon photovoltaic effect, mid-wave infrared (MWIR) silicon photonics, broadband Raman effects, inverse Raman scattering, and periodically-poled silicon (PePSi). These novel effects and techniques could create a new paradigm for silicon photonics and extend its utility beyond the traditionally anticipated applications. © 2010 Copyright SPIE - The International Society for Optical Engineering.published_or_final_versionThe 2010 Conference of the International Society for Optical Engineering (SPIE) Photonics Europe, Brussels, Belgium, 12-16 April 2010. In Proceedings of SPIE, 2010, v. 7719, article no. 77190

Periodically poled silicon (PePSi) for efficient and electronically-tuned nonlinear optics in silicon

Periodically poled silicon (PePSi) induces substantial 2nd order optical nonlinearity and at the same time achieves quasi-phase matching. PePSi is made by alternating strain gradients along the waveguide using periodic arrangement of stressed cladding layers. © 2013 OSA.published_or_final_versio

Pixel super-resolution in optical time-stretch microscopy using acousto-optic deflector

Session - Biosensing and Bio-Manipulation Techniques II (BW2A): paper BW2A.7Bio-Optics: Design and Application (BODA)We present experimental demonstration of pixel super-resolution time-stretch imaging by high-speed agile-beam-steering with the use of synchronized acousto-optic deflector--enabling high-resolution imaging rate of 1MHz whereas relaxing the stringent requirement on extreme data acquisition. © 2015 OSApostprin

Theory of amplified dispersive Fourier transformation

Amplified dispersive Fourier transformation (ADFT) is a powerful technique that maps the spectrum of an optical pulse into a time-domain waveform using group-velocity dispersion (GVD) and simultaneously amplifies it in the optical domain. It replaces a diffraction grating and detector array with a dispersive fiber and single photodetector, greatly simplifying the system and, more importantly, enabling ultrafast real-time spectroscopic measurements. Here we present a theory of ADFT by deriving the general equation and spectral resolution for ADFT and studying the evolution of the pulse spectrum into time, the effect of GVD coefficients on ADFT, and the requirement for dispersion. This theory is expected to lend valuable insights into the process and implementation of ADFT. © 2009 The American Physical Society.published_or_final_versio

Dispersive Fourier transform using few-mode fibers for real-time and high-speed spectroscopy

Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications XIIDispersive Fourier Transform (DFT) is a powerful technique for real-time and high-speed spectroscopy. In DFT, the spectral information of an optical pulse is mapped into time using group velocity dispersion (GVD) in the dispersive fibers with an ultrafast real-time spectral acquisition rate (>10 MHz). Typically, multi-mode fiber (MMF) is not recommended for performing DFT because the modal dispersion, which occurs simultaneously with GVD, introduces the ambiguity in the wavelength-to-time mapping during DFT. Nevertheless, we here demonstrate that a clear wavelength-to-time mapping in DFT can be achieved by using the few-mode fibers (FMFs) which, instead of having hundreds of propagation modes, support only a few modes. FMF-based DFT becomes appealing when it operates at the shorter wavelengths e.g. 1-μm range-a favorable spectral window for biomedical diagnostics, where low-cost single mode fibers (SMFs) and high-performance dispersion-engineered fibers are not readily available for DFT. By employing the telecommunication SMFs (e.g. SMF28), which are in effect FMFs in the 1-μm range as their cut-off wavelength is ∼1260 nm, we observe that a 3nm wide spectrum can be clearly mapped into time with a GVD as high as -72ps/nm and a loss of 5 dB/km at a spectral acquisition rate of 20 MHz. Moreover, its larger core size than the high-cost 1-μm SMFs renders FMFs to exhibit less nonlinearity, especially high-power amplification is implemented during DFT to enhance the detection sensitivity without compromising the speed. Hence, FMF-based DFT represents a cost-effective approach to realize high-speed DFT-based spectroscopy particularly in the biomedical diagnostics spectral window. © 2012 SPIE.published_or_final_versio

Demonstration of minute continuous-wave triggered supercontinuum generation at 1 µm for high-speed biophotonic applications

Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XIUltra-broadband supercontinuum (SC) at 1-μm wavelength is regarded as diagnostics window in bio-photonics due to its large penetration depth in tissues and less Rayleigh scattering. Dispersive Fourier transform (DFT) is an important technique to realize the high-speed, ultra-fast and high-throughput spectroscopy. Thus, a stable light source with good temporal stability plays an important role in the bio-imaging and spectroscopy applications. We here demonstrate stabilized and enhanced SC generation at 1 μm by a minute continuous-wave (CW) triggering scheme. By introducing a weak CW (200,000 times weaker than the pump), a significant broadening in the SC bandwidth and an improvement in the temporal stability can be obtained. Over 8 dB gain is achieved in both blue and red edges and the SC spectrum can span from 900 nm to over 1300 nm with the CW trigger. We present the CW-triggered SC capability of enabling highspeed spectroscopy based on DFT at 1 μm. In regards to the performance of DFT, the wavelength-time mapping fluctuation reduced by 50% which is an indication of the improvement of the temporal stability. This triggering scheme allows, for the first time, 1-μm DFT at a spectral acquisition rate of 20 MHz with good temporal stability - paving the way toward realizing practical real-time, ultrafast biomedical spectroscopy and imaging.published_or_final_versio

Pixel super-resolution in serial time-encoded amplified microscopy (STEAM)

Paper no. CTu3J.4We propose pixel super-resolution serial time-encoded amplified microscopy (STEAM) for achieves high speed and high-resolution imaging - relaxing the stringent requirement on the digitizer bandwidth while preserving the ultrahigh frame-rate (>MHz). © 2012 OSA.published_or_final_versio

Dispersive fourier transform at 1 μm based on high-order modes in few-mode-fiber

Paper no. JTh2A.8We report that high-speed and real-time spectral acquisition is achieved by dispersive Fourier transform (DFT) in the 1-μm spectral window using the selectively-excited higher-order modes in the few-mode fibers (FMFs). © 2012 OSA.published_or_final_versio

Theory of amplified dispersive Fourier transformation

Amplified dispersive Fourier transformation (ADFT) is a powerful technique that maps the spectrum of an optical pulse into a time-domain waveform using group-velocity dispersion (GVD) and simultaneously amplifies it in the optical domain. It replaces a diffraction grating and detector array with a dispersive fiber and single photodetector, greatly simplifying the system and, more importantly, enabling ultrafast real-time spectroscopic measurements. Here we present a theory of ADFT by deriving the general equation and spectral resolution for ADFT and studying the evolution of the pulse spectrum into time, the effect of GVD coefficients on ADFT, and the requirement for dispersion. This theory is expected to lend valuable insights into the process and implementation of ADFT. © 2009 The American Physical Society.published_or_final_versio

Simultaneous mechanical-scan-free confocal microscopy and laser microsurgery

We demonstrate an endoscope-compatible single-fiber-based device that performs simultaneous confocal microscopy and high-precision laser microsurgery. The method is based on mapping of two-dimensional sample coordinates onto the optical spectrum and allows us to perform two-dimensional imaging and microsurgery without any mechanical movement of the probe or the sample. The technology holds promise for creating highly miniaturized endoscopes for applications such as brain tumor, pediatric, and endovascular surgeries where high-precision, small, and flexible probes are required. © 2009 Optical Society of America.published_or_final_versio