Development of Linear and Nonlinear Components for Integrated Optical Signal Processing

Optical processors have potentially a major advantage over electronic processors because of their tremendous bandwidth. Massive parallelism is another inherent advantage of optical processors. However, it is traditionally demonstrated with free space components and seldom used for integrated optical signal processing. In this thesis, we consider spatial domain signal processing in guided wave structures, which brings a new dimension to the existing serial signal processing architecture and takes advantage of the parallelism in optics. A novel class of devices using holograms in multimode channel waveguides is developed in this work. Linear optical signal processing using multimode waveguide holograms (MWHs) is analyzed. We focus on discrete unitary transformations to take advantage of the discrete nature of modes in multimode waveguides. We prove that arbitrary unitary transformations can be performed using holograms in multimode waveguides. A model using the wide-angle beam propagation method (WA-BPM) is developed to simulate the devices and shows good agreement with the theory. The design principle of MWH devices is introduced. Based on the design principle, BPM models are used to design several devices including a mode-order converter, a Hadamard transformer, and an optical pattern generator/correlator. Optical pattern generators are fabricated to verify the theory and the model. Also, the bandwidth and fabrication tolerance of MWH devices are also analyzed. Also, we examine the nonlinear optical switches which allow the integration of MWHs into modern optical communication networks. A simple optical setup using an imaged 2-D phase grating is developed for characterization of the complex third-order nonlinearity chi(3) to identify suitable nonlinear materials for integrated optical switches. This technique provides a reliable way to characterize chi(3) as new materials are constantly being developed. Finally, we demonstrate the concept of optical switching using XPM in segmented semiconductor optical amplifiers (SOA) based on the proven technology of semiconductor waveguides. Segmented SOA switches allow the counter-propagation of control and signal pulses in the switch and avoid the problem of parasitic oscillations encountered in high gain SOA switches. A prototype device is experimentally characterized to demonstrate the concept, and a model is developed to obtain optimal parameters for future devices

Variable-ratio power splitters using computer-generated planar holograms on multimode interference couplers

© 2009 Optical Society of AmericaThe definitive version of this paper is available at: http://dx.doi.org/10.1364/OL.34.000512DOI: 10.1364/OL.34.000512Variable-ratio power splitters using computer-generated planar holograms on multimode interference couplers are analyzed. The coherent wave at the device input is transformed to the desired output using numerically calculated refractive index perturbations on multimode channel waveguides at half the beat length. Devices are fabricated on the silicon-on-insulator platform and characterized at a wavelength of 1.55 μm . Power-splitting ratios are varied by changing the hologram etch depth and the hologram length

Vibrational Mode Multiplexing of Ultracold Atoms

Sending multiple messages on qubits encoded in different vibrational modes of cold atoms or ions along a transmission waveguide requires us to merge first and then separate the modes at input and output ends. Similarly, different qubits can be stored in the modes of a trap and be separated later. We design the fast splitting of a harmonic trap into an asymmetric double well so that the initial ground vibrational state becomes the ground state of one of two final wells, and the initial first excited state becomes the ground state of the other well. This might be done adiabatically by slowly deforming the trap. We speed up the process by inverse engineering a double-function trap using dynamical invariants. The separation (demultiplexing) followed by an inversion of the asymmetric bias and then by the reverse process (multiplexing) provides a population inversion protocol based solely on trap reshaping.This work was supported by the National Natural Science Foundation of China (Grant No. 61176118), Grants No. 12QH1400800 IT472-10, No. BFI-2010-255, No. 13PJ1403000, No. FIS2012-36673-C03-01, and the program UFI 11/55. S. M.-G. acknowledges support from a fellowship from UPV/EHU

Compact and self-aligned all-optical image correlator based on third-harmonic generation

© 2007 Optical Society of AmericaThe definitive version of this paper is available at: http://dx.doi.org/10.1364/OL.32.002599DOI: 10.1364/OL.32.002599We demonstrate a compact optical correlator using a diffractive optical element (DOE) beam splitter for 2D optical image processing. Image frequency conversion and correlation are demonstrated using third-harmonic generation (THG) in an organic film with a 1550nm femtosecond laser. Spatial and temporal alignment of the femtosecond pulses are obtained by imaging the DOE onto the organic film

Ultrafast optical image processing based on third-harmonic generation in organic thin films

© 2007 American Institute of Physics. The electronic version of this article is the complete one and can be found at: http://dx.doi.org/10.1063/1.2790826DOI: 10.1063/1.2790826We report on the use of the noncollinear third-harmonic generation in an amorphous polymer film operating in the eye safe and telecommunication compatible near-infrared range to perform ultrafast all-optical two-dimensional (2D) image processing at 1550 nm using 100 fs pulses. The background-free and nondegenerate outputs at 517 nm are easily spatially filtered and detected with low cost electronic components. We describe this Fourier transform based technique and demonstrate its application to the classical problem of 2D image recognition

Variable splitting ratio 2 × 2 MMI couplers using multimode waveguide holograms

© 2007 Optical Society of AmericaThe definitive version of this paper is available at: http://dx.doi.org/10.1364/OE.15.009015DOI: 10.1364/OE.15.009015Variable power splitting ratio 2×2 MMI couplers using multi-mode waveguide holograms are analyzed. Theoretical analysis shows that variable splitting ratios can be obtained with surface relief holograms on MMI couplers with fixed dimensions. Devices with paired-imaging lengths are designed on a silicon-on-insulator (SOI) platform. Beam propagation simulations are used to verify a matrix theory analysis and to investigate proposed device performance. Fabrication tolerance of the proposed device is also analyze

Nonlinear Refraction And Absorption In Highly Transmissive One-Dimensional Metal-Organic Photonic Bandgap Structures

We report on the optical properties of a metal-organic photonic bandgap structure showing a peak transmission ∼44 % and that enhances the nonlinear optical properties of bulk Copper by up to an order of magnitude. © 2008 Optical Society of America

Linear And Nonlinear Optical Properties Of Highly Transmissive One-Dimensional Metal-Organic Photonic Bandgap Structures

We present the design, fabrication and characterization of the optical properties of one-dimensional metal-organic photonic bandgaps (MO-PBGs) composed of a tetraphenyldiaminobiphenyl-based polymer and ultrathin electrically continuous Cu layers. The fabricated MO-PBGs achieve a peak transmission of around 44% at 620 nm combined with very large spectral, around 120 nm FWHM, and angular, more than 120° field-of-view, bandwidths. Using 140 fs pulses at various wavelengths we have found up to 10 × enhancements in the nonlinear optical (NLO) properties of the MO-PBGs when compared with the NLO response of ultrathin electrically continuous Cu layers