We propose, theoretically analyze and experimentally demonstrate a novel broadband operating Si-nanowire multistage delayed Mach-Zehnder interferometer (DMZI) based (De)MUXs utilizing wavelength insensitive couplers (WINCs) and the discrete phase shifters for the phase matching between cascade-connected DMZIs. Based on the coupled mode theory and transfer matrix method, the coupling characteristics of a Si-wire directional coupler (DC) and WINC are analytically discussed from the viewpoint of a wavelength sensitivity of coupling efficiency [κCoup(λ)]. We theoretically verify that the operating window of the proposed DeMUX can be as broad as >110 nm by introducing the WINC and the additional phase matching between multiple DMZIs. Based on the theoretical analysis, 300-mm waferscale ArF-immersion lithography process are used to fabricate the Si-wire-based 1×4Ch DeMUXs. It will be shown that >110-nm-wide operating window for the proposed DeMUXs with four kinds of channel spacings (Δν=400, 800, 1250, 1900GHz). The theoretically identified aspect of nearly constant κCoup(λ) by the WINC and the phase matching by the phase shifter is proven to be extremely effective way to make the production yield much better, because DeMUX spectral response keeps nearly constant even if insufficient fabrication accuracy makes spectral response be shifted toward longer or shorter wavelength side. In addition, it will be shown that operating spectral window could be made much wider by optimizing the WINC design parameters in the DeMUX configuration. The proposed scheme would be attractive for increasing available channel count without inducing any excessive losses, which makes the proposed scheme more practical in WDM optical transceivers.
Recently, grating couplers (GCs) have been extensively reported as a promising device for optical coupling between Siwire
waveguides and standard single mode optical fibers. In this paper, we report the feasibility study of Si-wire type
GCs fabricated by the 248-nm KrF lithography process on a 200-mm silicon-on-insulator (SOI) wafer with a 220-nmthick
Si layer. We report a 1D-GC for a transmitter that operates only with TE mode and a 2D-GC for a receiver that
splits arbitrary polarization from a single mode fiber operating at a wavelength of 1550 nm. We investigated the
fundamental feasibility with the simple design. Especially, the wafer uniformity in inter-dies of 1D and 2D-GC is mainly
examined on a 200-mm SOI wafer. Additionally, we experimentally clarify the fundamental characteristics of the 1DGC
from the viewpoint of an insertion loss and a 1-dB fiber misalignment tolerance. As for the 2D-GC, in addition to the
same aspects with the 1D-GC, an optical crosstalk and a polarization dependent loss will also be discussed around 1550
nm wavelength. Also, the center wavelength against a grating period of the 1D-GC and a circular hole diameter of the
2D-GC will be characterized.
We present flatband, low-loss and low-crosstalk characteristics of Si-nanowire-based 5th-order coupled resonator optical waveguides (CROW) fabricated by ArF-immersion lithography process on a 300-mm silicon-on-insulator (SOI) wafer.
We theoretically specified why phase controllability over Si-nanowire waveguides is prerequisite to attain desired
spectral response, discussing spectral degradation by random phase errors during fabrication process. It was
experimentally demonstrated that advanced patterning technology based on ArF-immersion lithography process showed
extremely low phase errors even for Si-nanowire channel waveguides. As a result, the device exhibited extremely low
loss of <0.2dB and low crosstalk of <-40dB without any external phase compensation. Furthermore, fairly good spectral
uniformity for all fabricated devices was found both in intra-dies and inter-dies. The center wavelengths for box-like
drop channel responses were distributed within 0.4 nm in the same die. This tendency was kept nearly constant for other
dies on the 300-mm SOI wafer. In the case of the inter-die distribution where each die is spaced by ~3cm, the deviation
of the center wavelengths was as low as ±1.8 nm between the dies separated by up to ~15 cm. The spectral superiority was reconfirmed by measuring 25 Gbps modulation signals launched into the device. Clear eye openings were observed as long as the optical signal wavelengths are stayed within the flat-topped passband of the 5th-order CROW. We believe these high-precision fabrication technologies based on 300-mm SOI wafer scale ArF-immersion lithography would be promising for several kinds of WDM multiplexers/demultiplexers having much complicated configurations and requiring much finer phase controllability.
A silicon (Si)-based, large-scale optical I/O chip will be a key device for a large-bandwidth, low-cost optical
interconnection employed in future high-performance computing systems. For these Si optical I/O chips, a significant
improvement in energy cost is strongly expected, hence, the use of micro ring-resonator (RR) based modulator is
assumed to be a promising approach. In order to handle a narrow and temperature-dependent operation bandwidth of the
RR-based modulator, we have proposed a novel Si transmitter that uses a cascaded RR MZ modulator and RR-based Si
hybrid laser. The RR-based Si hybrid laser is an external cavity laser integrating an InP SOA and a Si mirror chip
comprising a RR and DBR mirror. The SOA is flip-chip bonded to the Si mirror chip utilizing a precise flip-chip
bonding technology. The fabricated Si hybrid laser exhibited a low threshold current of 9.4mA, a high output power of
<15 mW, and a large wall-plug efficiency of 7.6% at 20°C. In addition, the device maintained a stable single longitudinal
mode lasing and a low RIN level of <-130 dB/Hz for 20-60°C. We also fabricated an integrated Si transmitter combining
a cascaded RR MZ modulator and RR-based Si hybrid laser. The 20-RR cascaded MZ modulator exhibited a 1-nm
operation bandwidth using multiple low-Q RRs. The modulator was driven with 10Gbps PRBS signal. For a temperature
range between 25 and 60°C, the lasing wavelength exhibited a red-shift of 2.5 nm, nevertheless, we confirmed clear eye
openings without adjusting the operating wavelength of the modulator.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.