Browsing by Author "Miller, D. A. B."

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Open Access
Digital Fourier optics
(Optical Society of America, 1996-03-10) Özaktaş, Haldun M.; Miller, D. A. B.
Analog Fourier optical processing systems can perform important classes of signal processing operations in parallel, but suffer from limited accuracy. Digital–optical equivalents of such systems could be built that share many features of the analog systems while allowing greater accuracy. We show that the digital equivalent of any system consisting of an arbitrary number of lenses, filters, spatial light modulators, and sections of free space can be constructed. There are many possible applications for such systems as well as many alternative technologies for constructing them; this paper stresses the potential of free-space interconnected active-device-plane-based optoelectronic architectures as a digital signal processing environment. Implementation of the active-device planes through hybridization of optoelectronic components with silicon electronics should allow the realization of systems whose performance exceeds that of purely electronic systems.
Open Access
High-efficiency p-i-n photodetectors on selective-area-grown Ge for monolithic integration
(Institute of Electrical and Electronics Engineers, 2009) Yu, H.-Y.; Ren, S.; Jung, W. S.; Okyay, Ali Kemal; Miller, D. A. B.; Saraswat, K. C.
We demonstrate normal incidence p-i-n photodiodes on selective-area-grown Ge using multiple hydrogen annealing for heteroepitaxy for the purpose of monolithic integration. An enhanced efficiency in the near-infrared regime and the absorption edge shifting to longer wavelength is achieved due to 0.14% residual tensile strain in the selective-area-grown Ge. The responsivities at 1.48, 1.525, and 1.55 μ are 0.8, 0.7, and 0.64 A/W, respectively, without an optimal antireflection coating. These results are promising toward monolithically integrated on-chip optical links and in telecommunications. © 2009 IEEE.
Open Access
Integrated photonic switches for nanosecond packet-switched optical wavelength conversion
(Optical Society of America, 2006) Fidaner, O.; Demir, Hilmi Volkan; Sabnis, V. A.; Zheng, J. F.; Harris, J. S.; Miller, D. A. B.
We present a multifunctional photonic switch that monolithically integrates an InGaAsP/InP quantum well electroabsorption modulator and an InGaAs photodiode as a part of an on-chip, InP optoelectronic circuit. The optical multifunctionality of the switch offers many configurations to allow for different optical network functions on a single chip. Here we experimentally demonstrate GHz-range optical wavelength-converting switching with only ~10 mW of absorbed input optical power, electronically controlled packet switching with a reconfiguration time of <2.5 ns, and optically controlled packet switching in <300 ps. ©2006 Optical Society of America
Open Access
Intimate monolithic integration of chip-scale photonic circuits
(IEEE, 2005) Sabnis, V. A.; Demir, Hilmi Volkan; Fidaner, O.; Zheng, J.-F.; Harris, J. S.; Miller, D. A. B.; Li, N.; Wu, T.-C.; Chen, H.-T.; Houng, Y.-M.
In this paper, we introduce a robust monolithic integration technique for fabricating photonic integrated circuits comprising optoelectronic devices (e.g., surface-illuminated photodetectors, waveguide quantum-well modulators, etc.) that are made of completely separate epitaxial structures and possibly reside at different locations across the wafer as necessary. Our technique is based on the combination of multiple crystal growth steps, judicious placement of epitaxial etch-stop layers, a carefully designed etch sequence, and self-planarization and passivation steps to compactly integrate optoelectronic devices. This multigrowth integration technique is broadly applicable to most III-V materials and can be exploited to fabricate sophisticated, highly integrated, multifunctional photonic integrated circuits on a single substrate. As a successful demonstration of this technique, we describe integrated photonic switches that consume only a 300 x 300 mu m footprint and incorporate InGaAs photodetector mesas and InGaAsP/InP quantum-well modulator waveguides separated by 50 mu m on an InP substrate. These switches perform electrically-reconfigurable optically-controlled wavelength conversion at multi-Gb/s data rates over the entire center telecommunication wavelength band.
Open Access
Limit to bit-rate capacity of electrical interconnects from aspect ratio of system architecture
(Academic Press, 1997-02-25) Miller, D. A. B.; Özaktaş, Haldun M.
We show that there is a limit to the total number of bits per second,B, of information that can flow in a simple digital electrical interconnection that is set only by the ratio of the lengthlof the interconnection to the total cross-sectional dimensionof the interconnect wiring—the “aspect ratio” of the interconnection. This limit is largely independent of the details of the design of the electrical lines. The limit is approximatelyB∼BoA/l2bits/s, withBo∼ 1015(bit/s) for high-performance strip lines and cables, ∼1016for small on-chip lines, and ∼1017–1018for equalized lines. Because the limit is scale-invariant, neither growing nor shrinking the system substantially changes the limit. Exceeding this limit requires techniques such as repeatering, coding, and multilevel modulation. Such a limit will become a problem as machines approach Tb/s information bandwidths. The limit will particularly affect architectures in which one processor must talk reasonably directly with many others. We argue that optical interconnects can solve this problem since they avoid the resistive loss physics that gives this limit.
Open Access
Multifunctional integrated photonic switches
(Institute of Electrical and Electronics Engineers, 2005) Demir, H. M.; Sabnis, V. A.; Fidaner, O.; Zheng, J.-F.; Harris, J. S.; Miller, D. A. B.
Traditional optical-electronic-optical (o-e-o) conversion in today’s optical networks requires cascading separately packaged electronic and optoelectronic chips and propagating high-speed electrical signals through and between these discrete modules. This increases the packaging and component costs, size, power consumption, and heat dissipation. As a remedy, we introduce a novel, chip-scale photonic switching architecture that operates by confining high-speed electrical signals in a compact optoelectronic chip and provides multiple network functions on such a single chip. This new technology features low optical and electrical power consumption, small installation space, high-speed operation, two-dimensional scalability, and remote electrical configurability. In this paper, we present both theoretical and experimental discussion of our monolithically integrated photonic switches that incorporate quantum-well waveguide modulators directly driven by on-chip surface-illuminated photodetectors. These switches can be conveniently arrayed two-dimensionally on a single chip to realize a number of network functions. Of those, we have experimentally demonstrated arbitrary wavelength conversion across 45 nm and dual-wavelength broadcasting over 20 nm, both spanning the telecommunication center band (1530–1565 nm) at switching speeds up to 2.5 Gb/s. Our theoretical calculations predict the capability of achieving optical switching at rates in excess of 10 Gb/s using milliwatt-level optical and electrical switching powers.
Open Access
Optoelectronic switches based on diffusive conduction
(AIP Publishing LLC, 2006) Demir, Hilmi Volkan; Koklu, H.; Yairi, M. B.; Harris, J. S.; Miller, D. A. B.
We study the process of diffusive conduction that we use in our optoelectronic switches to achieve rapid optical switching (on a picosecond time scale). We present the characteristic Green's function of the diffusive conduction derived for arbitrary initial conditions. We also report the series solutions of the diffusive conduction obtained for different boundary conditions (V=0 and del V=0 along the device contact lines) in different device geometries (rectangular and circular mesas). Using these analytical results, we investigate the effect of boundary conditions on the switching operation and the steady state behavior in optical links. We demonstrate the feasibility of using such diffusive conductive optoelectronic switches to establish optical links in return-to-zero and non-return-to-zero coding schemes. For multichannel optical switching, we discuss possible use of a single optoelectronic switch to accommodate multiple channels at once, with > 100 optical channels (with a 2000 mm(-2) channel density and < 10% cross-talk), predicted on a 300x300 mu m(2) mesa with a device switching bandwidth of > 50 GHz, leading to a 5 Tb/s aggregate transmission in principle. This approach of using multiple parallel channels on a single switch is completely opposite to the traditional idea of arraying many switches. This proposed scheme eliminates the need for on-chip switch integration and the need for the alignment of the optical channels to the integrated individual switches.
Open Access
Scalable wavelength-converting crossbar switches
(IEEE, 2004-10) Demir, Hilmi Volkan; Sabnis, V. A.; Zheng, J. F.; Fidaner, O.; Harris, J. S.; Miller, D. A. B.
We report scalable low-power wavelength-converting Crossbar switches that monolithically integrate two-dimensional compact arrays of surface-normal photodiodes with quantum-well waveguide modulators. We demonstrate proof-of-concept, electrically reconfigurable 2 x 2 crossbars that perform unconstrained wavelength conversion across 35 nm in the C-band (1530-1565 nm), using only <4.3-mW absorbed input optical power, and with 10-dB extinction ratio at 1.25 Gb/s. Such wavelength-converting crossbars provide complete flexibility to selectively convert any of the input wavelengths to any of the output wavelengths at high data bit rates in telecommunication, with the input and output wavelengths being arbitrarily chosen within the C-band.
Open Access
Self-aligned via and trench for metal contact in III-V semiconductor devices
(AIP Publishing LLC, 2006) Zheng, J. F.; Demir, Hilmi Volkan; Sabnis, V.A.; Fidaner, O.; Harris, J.S.; Miller, D. A. B.
A semiconductor processing method for the formation of self-aligned via and trench structures in III-V semiconductor devices (in particular, on InP platform) is presented, together with fabrication results. As a template for such self-aligned via and trench formations in a surrounding polymer layer on a semiconductor device, we make use of a sacrificial layer that consists of either a Si O2 dielectric hard mask layer deposited on the device layers or a sacrificial semiconductor layer grown on top of the device epitaxial layers (e.g., InP on an InGaAs etch stop), both laid down on the device layers before patterning the device geometry. During the semiconductor device etching, the sacrificial layer is kept as a part of the patterned structures and is, therefore, perfectly self-aligned. By selectively removing the sacrificial layer surrounded by the polymer that is etched back within the thickness of the sacrificial layer, an opening such as a via and a trench is formed perfectly self-aligned on the device top area in the place of the sacrificial layer. This process yields a pristine semiconductor surface for metal contacts and fully utilizes the contact area available on the device top, no matter how small the device area is. This approach thus provides as low an Ohmic contact resistance as possible upon filling the via and the trench with metal deposition. The additional use of a thin Si3 N4 protecting layer surrounding the device sidewalls improves the robustness of the process without any undesired impact on the device electrical passivation (or on the optical mode characteristics if the device also includes a waveguide). This method offers metal contacts scalable to the device size, being limited only by the feasible device size itself. This method is also applicable to the fabrication of other III-V based integrated devices.
Open Access
Self-aligning planarization and passivation for integration applications in III-V semiconductor devices
(IEEE, 2005) Demir, Hilmi Volkan; Zheng, J.-F.; Sabnis, V. A.; Fidaner, O.; Hanberg, J.; Harris, J. S.; Miller, D. A. B.
This paper reports an easy planarization and passivation approach for the integration of III-V semiconductor devices. Vertically etched III-V semiconductor devices typically require sidewall passivation to suppress leakage currents and planarization of the passivation material for metal interconnection and device integration. It is, however, challenging to planarize all devices at once. This technique offers wafer-scale passivation and planarization that is automatically leveled to the device top in the 1-3-mum vicinity surrounding each device. In this method, a dielectric hard mask is used to define the device area. An undercut structure is intentionally created below the hard mask, which is retained during the subsequent polymer spinning and anisotropic polymer etch back., The spin-on polymer that fills in the undercut seals the sidewalls for all the devices across the wafer. After the polymer etch back, the dielectric mask is removed leaving the polymer surrounding each device level with its device top to atomic scale flatness. This integration method is robust and is insensitive to spin-on polymer thickness, polymer etch nonuniformity, and device height difference. It prevents the polymer under the hard mask from etch-induced damage and creates a polymer-free device surface for metallization upon removal of the dielectric mask. We applied this integration technique in fabricating an InP-based photonic switch that consists of a mesa photodiode and a quantum-well waveguide modulator using benzocyclobutene (BCB) polymer. We demonstrated functional integrated photonic switches with high process yield of >90%, high breakdown voltage of >25 V, and low ohmic contact resistance of similar to 10 Omega. To the best of our knowledge, such an integration of a surface-normal photodiode and a lumped electroabsorption modulator with the use of BCB is the first to be implemented on a single substrate.