In this work, we present for the first time a partially slotted silicon ring resonator (PSRR) covered with an electro-optical polymer (Poly[(methyl methacrylate)-co-(Disperse Red 1 acrylate)]). The PSRR takes advantage of both a highly efficient vertical slot waveguide based phase shifter and a low loss strip waveguide in a single ring. The device is realized on 200 mm silicon-on-insulator wafers using 248 nm DUV lithography and covered with the electro-optic polymer in a post process. This silicon-organic hybrid ring resonator has a small footprint, high optical quality factor, and high DC device tunability. A quality factor of up to 105 and a DC device tunability of about 700 pm/V is experimentally demonstrated in the wavelength range of 1540 nm to 1590 nm. Further, we compare our results with state-of-the-art silicon-organic hybrid devices by determining the poling efficiency. It is demonstrated that the active PSRR is a promising candidate for efficient optical switches and tunable filters.
KEYWORDS: Transceivers, Transmitters, Energy efficiency, Electronics, Modulation, Sensors, Signal attenuation, Silicon, Manufacturing, Receivers, Modulators, Photonics, Diodes, Silicon photonics, Data centers, Optical interconnects, Back end of line
We report on an ultra-compact co-integrated transmitter and receiver in SiGe BiCMOS technology for short reach optical interconnects. A fully integrated EPIC transceiver chip on silicon photonics technology is described. The chip integrates all photonic and electronic devices for an electro-optic transceiver and has been designed to be testable on wafer-scale. A node-matched diode modulator based on carrier injection is a key building block in the chip design. Its operation performance is presented with respect to insertion loss, signal-to-noise-ratio and power consumption at a 25.78125 Gbit/s in NRZ operation. A novel SiGe based photodetector exhibits a -3 dB bandwidth of up to 70 GHz and a responsivity of >1 A/W. Details are given about the process technology of co-integration of photonic and electronic integrated circuits using both silicon-on-insulator and bulk silicon. The implemented co-integration process requires only few additional process steps, leading to only a slight increase in complexity compared to conventional CMOS and BiCMOS baselines.
Passive and tunable optical filters as well as optical modulators, directly fabricated on the end-faces of optical fibers can
provide a fast and low cost production. A hybrid layer system can be built up to a passive Fabry-Pérot microcavity,
where alternating dielectric high and low refractive materials are used as mirrors and a highly transparent polymer as the
spacer material. The mirror design and the spacer thickness define the center operation wavelength and the filter
bandwidth. Bandwidths of less than 1 nm (FWHM) at a wavelength of 1560 nm could be achieved for such microcavities
on the end-faces of optical fibers.
Enhancing the hybrid layer system by transparent conductive electrodes and by adding electro-optically active
chromophores to the polymeric spacer material, the filters become tunable. The material used for the electrodes is indium
tin oxide (ITO). The oxidic electrodes have to be merged with the dielectric mirrors and the polymeric spacer. Applying
a voltage to the electro-optically active polymeric spacer utilizing such electrodes, the refractive index of the spacer can
be changed and therefore the resonance criteria of the microcavity.
Raman scattering in planar silicon on insulator (SOI) waveguides with 2 μm width, 220 nm height and
2 cm length is investigated. A cw Nd:YAP laser at 1340.6 nm with 7 GHz FWHM spectral width is
used as the pump source. A lensed fiber of 2.5 μm focus diameter is used to couple the pump laser into
the waveguide. The coupling efficiency is estimated to be around 10%. Spontaneous Raman scattering
is observed with as low as 2.5 mW pump power inside the waveguide. The spontaneous Raman
spectrum is measured by an optical spectrum analyzer. The first order Raman peak is measured at
around 1441.4 nm corresponding to a Raman shift of 15.6 THz, while the FWHM of Raman spectrum
is measured as around 100 GHz. Maximum Raman output of around 90 pW is obtained by around 22
mW pump. The stimulated Raman gain coefficient is estimated as around 56 cm/GW from the
relationship between spontaneous Raman output power and pump power. A temperature dependence of
Raman frequency shift of about 0.6 GHz/K is measured. The spontaneous anti-Stokes Raman scattering
output peak at 1253 nm is also observed with around 35 mW pump. Stimulated Raman amplification
measurement is carried out with a SLED white light source as probe signal. With 35 mW pump power,
around 0.6 dB gain has been determined with both pump and probe being TE polarized.
We have designed, fabricated and investigated one-dimensional (1D) micro-cavities in Silicon-on-Insulator (SOI)
waveguides. The single mode waveguides are fabricated in a 220 nm silicon device layer. The 1D micro-cavities in
Fabry-Perot structure consist of two Bragg-mirror regions formed by a sinusoidal modulation of the waveguide width.
The mirror regions are separated by a sub-micron spacer.
The SOI photonic structures are produced in a CMOS environment using 248 nm DUV lithography. The waveguides as
well as the width modulated mirror regions are designed using a single mask and are fabricated in a shallow trench
The transmission spectra of these width modulated micro-cavities with different mirror reflectivities and cavity lengths
are investigated. Q-factors up to 855 could be observed at 1550 nm wavelength with low insertion loss of 1.9 dB.
The width modulated micro-cavities, including the mirror regions, have lengths of less than 20 microns and widths of
maximum 450 nm. These small foot-print cavities act as band pass filters and can be used as resonators for laser or
electro-optic modulation of light.
We have developed thin film Fabry-Perot filters directly coated on optical fibers to archive a high level of integration
with a reduction of optical elements. Such band-pass filters can be used in fiber optical sensor systems, and for fiber
communication, e.g. CWDM applications.
The filters cavities consist of a single spacer and two dielectric mirrors. The dielectric mirrors are deposited by PVD
directly on end-faces of single-mode optical fibers. Dielectric as well as polymeric materials were applied as the spacer
layer. Polymeric spacer layers were deposited by dip coating.
The influence of the mirror reflectivity on the transmission band of the Fabry-Perot filters was investigated. Furthermore,
the optical performance of filters with first order (λ/2) as well as higher order spacers was analyzed. The experimental
results are compared with numerical analysis of Fabry-Perot cavities on the end-face of cylindrical waveguides. The
spectral characteristic of the filters are calculated using a software solving Maxwell´s equations by a FDTD method.
The layer design of the filters and the deposition process were optimized for maximum transmission and narrow
bandwidth of the transmission peak. Passive band-pass filters on fiber end-faces were designed, fabricated and
characterized for transmission wavelengths of 945 nm, 1300 nm, as well as 1550 nm. Bandwidths as narrow as 1 nm
could be achieved for 945 nm.
We have investigated microcavities in Silicon-on-Insolator (SOI) waveguides. The rectangular waveguides with 500 nm
width are fabricated in the 220 nm silicon device layer. The microcavities are formed by one-dimensional photonic
crystals in Fabry-Perot structure directly written in the waveguides.
The SOI photonic structures are produced in a CMOS environment using 248 nm DUV lithography, where the
waveguides as well as the photonic crystals are created in the same step using a single mask.
In order to achieve a desired spectral shape of the filter function capable for several applications, a number of different
cavities were investigated, e.g. single cavities of first and higher order as well as multi-cavity filters.
The experimental results are compared with simulations of photonic crystal microcavities in strip waveguides. The
spectral transmission function of such filters dependent on the design parameters are calculated by an analysis based on
Finite-Difference-Time-Domain (FDTD) method.
We have developed thin film Fabry-Perot filters directly coated on fiber end-faces. The layer design of the filters and the deposition process were optimized for maximum transmission, and the width of the transmission peak. The optical performance of Fabry-Perot filters deposited on fiber end-faces of single-mode as well as multimode optical fibers have been investigated. We have performed laser-induced damage threshold (LIDT) measurements on the multi-layer systems to optimize the fiber preparation before deposition. The multi-layer systems were analyzed by means of atomic force microscopy and scanning electron microscopy.
Five different multimode optical fibers have been coated with an antireflective coating to minimize transmission losses. The transmission, the stimulated Brillouin scattering (SBS) threshold and the laser-induced damage threshold (LIDT) were determined for the fibers. The measurements are performed at 1064 nm with 24 ns pulse duration. Fiber transmissions reach up to >99.5% for optimal laser beam coupling. A damage threshold of up to 125 J/cm2 could be achieved. The fiber coatings were investigated using atomic force microscopy and scanning electron microscopy.
Multimode optical fibers are used for the transmission of high power laser pulses and as phase conjugated mirrors by stimulated Brillouin scattering. Both applications are enhanced by antireflection coatings on the fiber end-faces. Fiber transmissions reach more than 99.5% for pulse energies below the threshold of stimulated Brillouin scattering. Laser-induced damage thresholds of the fibers coated with Ta2O5 / SiO2 were measured at 1064 nm and 24 ns pulse duration. A damage threshold of up to 101 J/cm2 could be achieved. The damage morphology was investigated using atomic force microscopy and scanning electron microscopy.
Standard 200 μm multimode fibers with Ta2O5/SiO2 antireflective coatings reach a transmission of more than 99.5% below the threshold of stimulated Brillouin scattering. The laser-induced damage threshold measured at 1064 nm and 24 ns pulse duration was about half than the LIDT of uncoated fibers.
For the development of standard measurement procedures in optics characterization, comparative measurement campaigns (Round-robin experiments) are indispensable. Within the framework of the CHOCLAB project in the mid-90s, several international Round-robins were
successfully performed qualifying procedures for e. g. 1 on 1-LIDT, laser-calorimetry and total scattering. During the recent years, the demand for single pulse damage investigations has been overtaken by the more practically relevant S on 1-LIDT. In contrast to the
industrial needs, the comparability of the multiple-pulse LIDT has not been proven by Round-robin experiments up to now. As a consequence of the current research activities on the interaction of ultra-short pulses with matter as well as industrial applications, numerous fs-laser systems become available in universities and research institutes. Furthermore, special problems for damage testing may be expected because of the intrinsic effects connected with the interaction of ultrashort pulses with optical materials. Therefore, a Round-robin experiment on S on 1-damage testing
utilizing fs-pulses was conducted within the framework of the EUREKA-project CHOCLAB II. For this experiment, seven parties investigated different types of mirrors and windows. Most of the partners were guided by the International Standard ISO 11254-2, but one partner employed his own damage testing technique. In this presentation, the results of this comparative experiment are compiled demonstrating the problems induced by special effects of damage testing in the ultra-short pulse regime.