Integration of Optoelectronic and RF Devices for Applications in Optical Interconnect and Wireless Communication

Integration of Optoelectronic and RF Devices for Applications in Optical Interconnect and Wireless Communication Zhaoran (Rena) Huang Assistant Professor Department of Electrical, Computer and System Engineering Rensselaer Polytechnic Institute

Outline Substrate removed thin film optoelectronic device Application of thin-film optoelectronic device for chip-to-chip optical interconnect Embedded optical interconnect on PCB Board Integration of RF and Opto devices for dual-mode wireless communication

Planar Metal-Semiconductor-Metal Photodetector MSM Structure: Contact pads MSM electrodes (fingers) semiconductor Front illumination Back illumination + - + Light Absorbing layer Substrate

Fabrication of Inverted Thin Film Optoelectronic Devices MSM PD Wafer 40nm InAlAs cap layer 50nm InGaAlAs composition grade 740nm InGaAs absorbing layer 50nm InGaAlAs composition grade 40nm InAlAs buffer layer Inverted MSM PDs Host Substrate 200nm InGaAs etch stop InP substrate Thin film MSM PD: ~ 1µm thick, substrate removed MSM PDs and host substrates are separately optimized. Planar geometry with integrated thin film MSM PDs.

Outline Substrate removed thin film optoelectronic device Application of thin-film optoelectronic device for chip-to-chip optical interconnect Embedded optical interconnect on PCB Board Integration of RF and Opto devices for dual-mode wireless communication

Optical Interconnect for Signal Distribution Thin Film MSM PDs (receivers) Waveguide (central bus) High density substrate Ray Chen, UT Austin

Integration of Thin Film Optoelectronic Devices for Optical Interconnect Laser diode Receiver Circuit #1 Receiver Circuit #2 / / / λ 1 λ 2 Waveguide Polymer Embedded Grating coupler waveguide core photodetector (optional) SOP Substrate (Si/SiO 2, Ceramics and Organic Board) Au bumps claddings Thin film laser diodes and photodetectors are all embedded in polymer waveguide.

Integration of Thin Film Optoelectronic Devices for Optical Interconnect Laser diode Receiver Circuit #1 Receiver Circuit #2 / / / λ 1 λ 2 Waveguide Polymer Au bumps Grating waveguide core coupler SOP Substrate (Si/SiO 2, Ceramics and Organic Board) Integrated photodetector claddings Thin film laser diodes are embedded in polymer waveguide. Photodetectors are bonded to the CMOS receiver.

Integration of Thin Film MSM PD on Various Substrates Si/SiO 2 Substrate Ceramic Substrate CMOS Substrate CMOS Substrate PCB Board Z. Huang, et. al., EL, 2002 Z. Huang, LEOS summer topical, 2004

Embedded Planar Thin Film MSM PD for Optical Interconnect Waveguide (3 channels) I-MSM PD (200/200µm) SiO 2 substrate Tested data rate at 1 Gbps FWHM: 26.5 ps, Bandwidth ~ 12GHz Polymer waveguide I-MSM PD (40/40µm) Ceramic substrate

Integration of Thin Film MSM PD On Si CMOS Chip PD on a 400 Mbps photoreceiver PD size: 200/200 μm Finger width: 2 μm Finger gap: 2 μm PD on 10 Gbps photoreceiver PD size: D = 40 μm Finger width: 1 μm Finger gap: 1 μm

Other Applications: Vertical Stacked Thin Film Optoelectronic Devices Bi-directional optical link: Thin film LED I-MSM PD D. Geddis, et. al., pp 455, PTL, 2003

Outline Substrate removed thin film optoelectronic device Application of thin-film optoelectronic device for chip-to-chip optical interconnect Embedded optical interconnect on PCB Board Integration of RF and Opto devices for dual-mode wireless communication

High Speed Optical Interconnect for Backplane Communication In chip ~ 1 cm box rack-to-rack ~ 3 m chip-to-chip MCM ~ 10 cm rack Back Plane box-to-box ~ 50 m chip-to-chip on Board ~ 50 cm High data rate Free from EMI

Embedded Bare Die Chip Packaging for High Speed Optical Interconnects Low cost: bare die devices are commercially available and lifetime tested. Good reliability: thickness > 100μm easy to handle. High density package: smaller chip foam factor Optical waveguide Laser driver EEL core buffer layer PiN / MSM TIA L/A PCB

Embedded Optoelectronic Bare Die Chips in Polymer Optical Waveguide Embedded Laser on board Embedded PiN PD on board Bare-die laser drive chip on PCB Bare-die TIA chip on PCB

Demonstration Coupling of End-to-End Efficiency Measurement Optical Link on Setup PCB Board λ = 1.3μm 1 cm radius detector laser probes 5 cm long 50 um x 50 um waveguide probes PWB Infrared image of laser diode-waveguide-photodetector optical link

Bit Rate Test External for Bias-T the laser Embedded driver (50 Ω) End-to-End Single Optical ended L/A Link output 5 Gpbs optical link 7 Gpbs optical link Transmitter and Receiver has reached 10Gbps at separate testing. Data rate is limited by coupling efficiency at various stages 9 Gpbs optical link

Outline Substrate removed thin film optoelectronic device Application of thin-film optoelectronic device for chip-to-chip optical interconnect Embedded optical interconnect on PCB Board Integration of RF and Opto devices for dual-mode wireless communication

Applications of Wireless Sensor Network Mesh sensor network Last mile broadband access network Smart building Other applications: military, battle field, surveillance

RF or Free Space Optical Link? Property of Medium RF FSO Comments on FSO Bandwidth FCC Regulated? Yes No Approval not required; Worldwide compatibility. Passing Through Walls? Yes No Less coverage but more secured; Independent links in different rooms. Path Loss High High High requirement on alignment; scattering loss Dominant Noise Other Users Background Noise Limited Range Alignment Power Consumption of the Link Low requirement High Usually sensitive Low

Power Consumption of FSO Wireless Link at 2.5Gbps Laser Driver Laser Diode λ atmosphere λ Photodiode TIA L/A MAX 3930 (Maxim) VCSEL (Optowell) PiN (Optowell) MAX 3866 (Maxim) Parameter Specification: Laser driver: P 28mW VCSEL Laser diode: P max =2.5mW; η=0.4; I th =1.5mA; θ=14 0 ~30 0 Photodiode: ρ=0.6a/w; D=100μm TIA-L/A: I n =433nA; P=165mW PIN Total power consumption = ~ 200mW (NR OOK) at 2.5Gbps Energy consumption per bit = 1.4 10-7 mj/bit

A Commercial Sensor Node Operating at 2.4GHz Frequency Band Commercial Sensor Node Tmote-Sky (Moteiv Corporation): horizontal mount vertical mount Antenna: Inverted F-antenna Data rate: 150kbits Radiation pattern

FSO and RF Wireless Links FSO Link: Laser Driver Laser Diode λ atmosphere λ Photodiode TIA L/A RF Link: transmitter Low-Noise Amplifier ADC Pulse Shaping Modulator Carrier Down Converter receiver Carrier Power Amplifier ADC Demodulator Equalizer DAC FSO Power consumption 200mW (NR OOK) at 2.5Gbps 113mW (O-QPSK) at 250kbps Energy/bit 1.4 10-7 mj/bit 2.03 10-4 mj/bit RF

Microwave Attenuation in Atmosphere Local minima of microwave attenuation occurs at bands of 25~40GHz, and 70~100GHz High attenuation spectrum reuse

Miniaturized on-chip RF and Optical Free Space Wireless Communication Module Application: dense sensor networks, smart building, surveillance, battle field, net-centric operation Approach: Monolithic integrated RF and optical elements on SiGe substrate State-of-the-Art Technologies RPI Vision: 3D Integration of a Single Sensor Node λ antenna Communication module MMIC Control Sensor Chip OEIC Adhesion layer CHORD > 4 inches Mote 2 1 inches Power harvest module Hybrid package, assembled on PCB board Large, bulky and high power consumption Less than 3mm 3mm Miniaturization: significant advantages in size, weight and power Minimal interconnects and manual assembly: reduced parasitics and assembly low cost More reliable and improved performance

Design of On-Chip Quasi-Yagi Antenna with Optical Elements Photodetector array (primary antenna director) Laser diode array (secondary antenna director) λ λ Antenna Adhesive LD λ Lens λ Si or SiGe Quasi-Yagi Antenna Ground Plane PD Side View Top View

Quasi-Yagi Antenna on Duroid Substrate Director Driver y y Ground Plane x z x Feed Duroid material: ε r = 10.2 Simulation is performed by CST microwave studio Far field Radiation Pattern at 10 GHz Main Lobe direction is parallel to y axis Broadband Gain (db) Broadband Gain Frequency (GHz) S11 (db) Return Loss Frequency (GHz) Main Lobe Direction (degree) Main Lobe Direction Frequency / GHz

Quasi-Yagi Antenna on Electromagnetic Bandgap Substrate Air Hole r 1 mm Broadband Gain Return Loss Broadband Gain (db) 6 5 4 3 2 1 0 6 7 8 9 10 11 12 13 14 Frequency (GHz) S1,1 (db) 0-5 -10-15 -20-25 6 7 8 9 10 11 12 13 14 Frequency (GHz) Gain enhancement is observed with EBG substrate. Structure is not optimized.

Effect of Vertical Vias to Quasi-Yagi Antenna Radiation Top View Side View Optical elements with bias through the substrate: z via x y x S-Parameters: Default vs. Default w/optical Elements at director antenna Communication module 0-5 MMIC Control OEIC Return Loss [db] -10-15 -20-25 -30-35 Default w/opto w/vias Sensor Chip Power harvest module -40 6 7 8 9 10 11 12 13 14 Frequency [GHz] Small variation is observed in the radiation pattern and the return loss simulation.

Integration of Optical Elements on Quasi-Yagi Antenna Substrate Integration of quasi-yagi antenna with optical bonding pads Power Input Laser Diode Photodetector Signal Output Integration with optical elements Simulation: Fabricated antenna Return Loss Broadband Gain Schematic illustration S11 (db) 0 6 7 8 9 10 11 12 13 14-5 -10-15 -20-25 -30-35 Broadband Gain (db) 8 7 6 5 4 3 2 1 0 6 7 8 9 10 11 12 13 14 Default w/ optical bonding pads Frequency (GHz) Frequency (GHz)

Simultaneous Operation of On-Chip Optical and RF Signal Transmission Laser diode Photodetector Effect of VCSEL to Return Loss 0-5 -10-15 -20-25 -30-35 -40 6 8 10 12 14 with wire/without clamp with wire/with clamp/power off with wire/with clamp/power on No cross-talk from the on-chip optoelectronics devices to the RF antenna

DC Characteristics of Laser Emission under RF Radiation P-I I-V The RF radiation has no noticeable effect on the DC characteristics of the laser emission.