David Mareš

WDM hybrid microoptical transceiver with Bragg volume grating

The paper presents the design, simulation and construction results of the wavelength division multiplex bidirectional transceiver module (WDM transceiver) for the passive optical network (PON) of a fiber to the home (FTTH) topology network. WDM transceiver uses a microoptical hybrid integration technology with volume holographic Bragg grating triplex filter -VHGT and a collimation lenses imagine system for wavelength multiplexing/ demultiplexing. This transmission type VHGT filter has high diffraction angle, very low insertion loses and optical crosstalk, which guide to very good technical parameters of transceiver module. WDM transceiver has been constructed using system of a four micromodules in the new circle topology. The optical micromodule with VHGT filter and collimation and decollimation lenses, two optoelectronics microwave receiver micromodules for receiving download information (internet and digital TV signals) and optoelectronic transmitter micromodule for transmitting upload information. In the paper is presented the optical analysis of the optical imagine system by ray-transfer matrix. We compute and measure VHGT characteristics such as diffraction angle, diffraction efficiency and diffraction crosstalk of the optical system for 1310, 1490 and 1550 nm wavelength radiation. For the design of optoelectronic receiver micromodule was used the low signal electrical equivalent circuit for the dynamic performance signal analysis. In the paper is presented the planar form WDM transceiver with polymer optical waveguides and two stage interference demultiplexing optical filter as well.

Acoustic phonons in unfilled tetragonal tungsten-bronze crystals

ABSTRACT We have studied several unfilled tetragonal tungsten-bronze crystals (SBN-35, CBN-28, CBN-30, CBN-32) by differential scanning calorimetry, Brillouin spectroscopy and piezoresponse-force microscopy. The Brillouin backscattering configuration in the c-plates revealed the longitudinal acoustic phonon, which has a frequency near 50 GHz and displays softening when approaching the phase transition in all crystals. The ferroelectric domain structure and the domain size are dependent on the Sr/Ba or Ca/Ba ratios, and on the occupation rate in the channels as shown by the piezoresponse-force microscopy images. A splitting of the longitudinal acoustic phonon was found in SBN-35 in the multidomain sample, but poling of the crystal removed this splitting and just left the phonon with higher frequency.

Design and optimization of the silver nanograting structure utilizing surface plasmon-polariton for increase of SERS sensor response

This paper reports on the design of the surface enhanced Raman spectroscopy (SERS) structures that were optimized through computation and simulation to obtain the best enhancement of the surface plasmon-polariton (SPP) response on these structures. The structure of the silver nano-grating was designed, fabricated, optimized and measured. The enhancement factor and the increase in the absorption capabilities associated with SPP were evaluated. The rigorous coupled wave analysis (RCWA) and finite-difference time-domain (FDTD) computational/simulation methods were utilized. The comparison between the computation simulation outputs and the measured outputs of the fabricated samples was performed.

Bi-directional triplexer with butterfly MMI coupler using SU-8 polymer waveguides

We report about a design of a bi-directional planar optical multiplex/demultiplex filter (triplexer) for the optical part of planar hybrid WDM bi-directional transceiver in fiber-to-the-home (FTTH) PON applications. The triplex lightwave circuit is based on the Epoxy Novolak Resin SU-8 waveguides on the silica-on-silicon substrate with Polymethylmethacrylate cladding layer. The triplexer is comprised of a linear butterfly concept of multimode interference (MMI) coupler separating downstream optical signals of 1490 nm and 1550 nm. For the upstream channel of 1310 nm, an additional directional coupler (DC) is used to add optical signal of 1310 nm propagating in opposite direction. The optical triplexer was designed and optimized using beam propagation method. The insertion losses, crosstalk attenuation, and extinction ratio for all three inputs/outputs were investigated. The intended triplexer was designed using the parameters of the separated DC and MMI filter to approximate the idealized direct connection of both devices.

Micro-optical insertion system for WDM transceiver

The paper deals with the design of an micro-optical part of a WDM transceiver based on the circle volume holographic grating triplexer (VHGT) topology. The work is focused on detail description of the bidirectional micro-optical insertion system, especially on the coupling in the transmission direction of the WDM transceiver optical part. This micro-optical wavelength distribution system is imagine transmission system consisted of collimating cylindrical lenses set in the circle topology with the VHGT filter placed in the middle of the circle. The topology is described by ray matrices equations, calculated using analytic and numeric methods and optically measured. Considering simulation and measurement results of micro-optical insertion system the influence of these characteristics on ray path attenuation, diffraction efficiency and transceiver performance is estimated. The paper also discusses limits and conditions of the laser asymmetrical beam focus into the input/output optical fiber.