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Congratulations to Tony and Paolo for this invited paper on integrated isolators and circulators. August 9, 2018 The transmission spectra of the isolator at 1549.5 nm for 40 mA of applied current showing 25 dB of optical isolation.

Optical isolators and circulators are extremely valuable components to have in photonic integrated circuits, but their integration with lasers poses significant design and fabrication challenges. These challenges largely stem from the incompatibility of magnetooptic material with the silicon or III-V platforms commonly used today for photonic integration. Heterogeneous integration using wafer bonding can overcome many of these challenges, and provides a promising path towards integrating…

Congratulations to Alan Liu on the publication of this analysis of alternative approaches to high levels of optical integration August 3, 2018 Alan Liu

We present a brief overview of the various leading platforms for photonic integration. Subsequently, we consider the possibility of a photonic integrated circuit platform utilizing epitaxially grown III–V material on silicon—without the need for wafer bonding, or an externally coupled laser. Finally, a technoeconomic analysis contrasting the aforementioned platforms will be presented.

Congratulations to Yating and team for selection as cover article and Editor's Choice on this article just published on low threshold, high speed quantum dot ring lasers. July 26, 2018 Illustration of one fabricated microring laser

Microring lasers feature ultralow thresholds and inherent wavelength-division multiplexing functionalities, offering an attractive approach to miniaturizing photonics in a compact area. Here, we present static and dynamic properties of microring quantum dot lasers grown directly on exact (001) GaP/Si. Effectively, a single-mode operation was observed at 1.3 μm with modes at spectrally distant locations. High temperature stability with T 0∼103 K has been achieved with a low threshold of 3 mA…

Congratulations to Daehwan Jung for winning Best Paper Award at OECC 2018! July 15, 2018 Dr. Daehwan Jung at OECC 2018

1.3 μm InAs quantum dot lasers on Si show a CW threshold current of 4.8 mA and extrapolated lifetimes of ten million hours at 35 °C and ~65,000 hours at 60 °C.

Intel Wins SEMI Award at SEMICON West for Process and Integration July 11, 2018 Dr. Thomas Liljeberg, senior director of R&D for Intel Silicon Photonics.

Intel has won SEMI’s 2018 Award for the Americas. SEMI honored the celebrated chipmaker for pioneering process and integration breakthroughs that enabled the first high-volume Integrated Silicon Photonics Transceiver. The award was presented yesterday at SEMICON West 2018.

We are using p-modulation doping to reduce the linewidth enhancement factor in Quantum Dot lasers. This is important for narrower linewidth lasers, lower chirping lasers and reduced reflection sensitivity lasers. June 21, 2018 The aH-factor as a function of temperature for p-doped (red) and undoped (blue) QD lasers. The linear curve-fittings (dashed lines) are the guide to the eye only.

This work reports on the ultra-low linewidth enhancement factor (aH-factor) of semiconductor quantum dot lasers epitaxially grown on silicon. Owing to the low density of threading dislocations and resultant high gain, an aH value of 0.13 that is rather independent of the temperature range (288 K–308 K) is measured. Above the laser threshold, the linewidth enhancement factor does not increase extensively with the bias current which is very promising for the realization of future integrated…

Achieving Unprecedented Frequency Control in Miniature Lasers April 25, 2018 Under the DODOS program, researchers from NIST, University of California at Santa Barbara, and the California Institute of Technology have made significant progress advancing chip-based integrated photonics and nonlinear optics to miniaturize optical synthesizer components. Combining a pair of frequency combs, several miniature lasers, and other compact optoelectronic components, the researchers were able to replicate the capabilities of a tabletop-sized optical frequency synthesizer on four microchips.

Only a few decades ago, finding a particular channel on the radio or television meant dialing a knob by hand, making small tweaks and adjustments to hone in on the right signal. Of course, we now take such fine tuning for granted, simply pressing a button to achieve the same effect. This convenience is enabled by radio frequency synthesis, the generation of accurate signal frequencies from a single reference oscillator. The need for better radar in World War II drove the development of radio…

The importance of reducing threading dislocation density on laser lifetime is detailed in this paper. April 16, 2018 Extrapolated quantum dot laser lifetime versus the threading dislocation density. Lasers from Ref. 8 were aged at 30 C. The dashed line is a linear fit.

We investigate the impact of threading dislocation density on the reliability of 1.3 lm InAs quantum dot lasers epitaxially grown on Si. A reduction in the threading dislocation density from 2.8108 cm2 to 7.3106 cm2 has improved the laser lifetime by about five orders of magnitude when aged continuous-wave near room temperature (35 C). We have achieved extrapolated lifetimes (time to double initial threshold) more than 10 106 h. An accelerated laser aging test at an elevated temperature (60…

A first for single-section QDML lasers on Si April 2, 2018 Front from the left: Arthur C. Gossard and John E. Bowers, back from the left: Daehwan Jung, Songtao Liu and Justin C. Norman

The first single-section quantum dot mode-locked laser directly grown on a CMOS-compatible silicon substrate has been produced by researchers in the US. Their achievement could open the door to much lower complexity, cheaper laser sources for future large-scale silicon photonic integrated circuits.

An invited summary of the prospects for quantum dot photonic integrated circuits has just been published. March 27, 2018 device lifetime (either extrapolated or measured) for lasers on Si operating in the continuous wave mode. The distinction is noted between historical results on miscut Si substrates and recent results on CMOS compatible on-axis (001) Si.

Direct epitaxial integration of III-V materials on Si offers substantial manufacturing cost and scalability advantages over heterogeneous integration. The challenge is that epitaxial growth introduces high densities of crystalline defects that limit device performance and lifetime. Quantum dot lasers, amplifiers, modulators, and photodetectors epitaxially grown on Si are showing promise for achieving low-cost, scalable integration with silicon photonics. The unique electrical confinement…

A new review paper on the exciting technology and applications of thin film LiNbO3 has just been published March 19, 2018 Schematically overview of a LNOI integrated optical chip

Lithium niobate on insulator (LNOI) technology is revolutionizing the lithium niobate industry, enabling higher performance, lower cost and entirely new devices and applications. The availability of LNOI wafers has sparked significant interest in the platform for integrated optical applications, as LNOI offers the attractive material properties of lithium niobate, while also offering the stronger optical confinement and a high optical element integration density that has driven the success…

A new paper on high performance 2 micron arrayed waveguide gratings has just been published. February 27, 2018 (a) Cross-section SEM of a single-mode Si waveguide. Micrographs (b) of an AWG and (c) of an AWG-ring.

Low-loss arrayed waveguide gratings (AWGs) are demonstrated at a 2.0-μm wavelength. These devices promote rapidly developing photonic applications, supported by the recent development of mid-infrared lasers integrated on silicon (Si). Multi-spectral photonic integrated circuits at 2.0-μm are envisioned since the AWGs are fabricated with the 500-nm-thick Si-on-insulator platform compatible with recently demonstrated lasers and semiconductor optical amplifiers on Si. Characterization with the…

Reducing dislocations in gallium arsenide on silicon templates January 23, 2018 Room-temperature PL spectra of GaAs PL samples grown on native GaAs, and three different GaAs/GaP/Si templates.

University of California Santa Barbara (UCSB) in the USA has been working to optimize gallium arsenide (GaAs) molecular beam epitaxy (MBE) on gallium phosphide on silicon (GaP/Si) [Daehwan Jung et al, J. Appl. Phys., vol122, p225703, 2017]. Normally, growth of GaAs on Si uses off-axis substrates in efforts to avoid anti-phase domains. On-axis silicon is preferred for compatibility with CMOS processing foundries. The lattice mismatch between GaAs and Si is ~4%, leading to dislocations.

Chao Xiang demonstrated a novel scissors design with widely tunable delays and large dynamic range. The device and performance are shown below: January 22, 2018 Layout of a 40 microresonator TTD device.

Abstract—We design, fabricate, and characterize ultra-low loss continuously tunable optical true time delay devices based on Si3N4 ring resonators in a side-coupled integrated spaced sequence of resonators (SCISSOR) structure. A large tunable delay range up to 3.4 ns is demonstrated using the Balanced SCISSOR delay tuning scheme, for a record loss of only 0.89 dB/ns of delay. By optimizing the coupler design a device delay bandwidth of over 10 GHz is achieved with over 0.5 ns maximum time…

An important paper on Epitaxial Quantum Dot lasers on silicon has just been published. December 18, 2017 Record high injection efficiency: 87% 

Important advances: 

  1. Record low threshold current density for growth on (100) Si: 198 A/cm^2 
  2. Record low threshold current for any F-P laser grown on Si
  3. Record high injection efficiency: 87%
  4. Record long lifetime: More than 10 M hours at 35 C.
Congratulations to Chong Zhang for an Invited Paper on the highest capacity transceiver on Si. December 12, 2017 2.56 Tbps Network on Chip

Silicon photonic integration is an enabling technology for power- and cost-effective optical interconnects in exascale performance computers and datacenters which require extremely low power consumption and dense integration for a higher interface bandwidth density. In this paper, we experimentally demonstrate a fully integrated optical transceiver network on a silicon substrate using heterogeneous integration. High performance on-chip lasers, modulators and photodetectors are enabled by…

Congratulations to Tony and Paolo for demonstrating broadband integrated MZI optical isolators with 100 nm tuning, which covers the entire S + C telecom bands. November 21, 2017 Paolo Pintus and Tong (Duanni) Huang

We demonstrate integrated optical isolators with broadband behavior for the standard silicon-on-insulator platform. We achieve over 20 dB of optical isolation across 18 nm of optical bandwidth. The isolator is completely electrically controlled and does not require a permanent magnet. Furthermore, we demonstrate the ability to tune the central operating wavelength of the isolator across 100 nm, which covers the entire S + C telecom bands. These devices show promise for integration in optical…

Congratulations to Tin for demonstrating a novel idea to make a very stable arbitrary microwave frequency generator! November 20, 2017 Tin Komljenovic

We demonstrate a technique to precisely control and stabilize the beat frequency of a photonic microwave signal generator based on beating the optical signals of two lasers on a high-speed photodetector. The approach does not require high-speed electronic circuitry, but allows the control of the generated signal frequency up to hundreds of GHz. The demonstrated technique can readily be integrated on a chip-scale device using heterogeneous silicon platform, opening possibilities for…

Congratulations to Justin Norman for winning Best Student Paper award at the 2017 IEEE International Photonics Conference October 24, 2017 Justin Norman

We report 1300 nm continuous wave lasing on an on-axis GaP/Si (001) virtual substrate operating up to 60°C with record low threshold current of 27 mA. Ridge and broad area lasers were fabricated with seven layers of p-modulation doped quantum dots and as-cleaved facets.

Congratulations to Alex Spott and colleagues for a postdeadline paper at the 2017 IEEE International Photonics Conference on the first Interband Cascade Laser on Silicon. October 12, 2017 Alexander Spott

We demonstrate the first interband cascade lasers heterogeneously integrated with silicon waveguides. The 3.6 μm wavelength lasers operate in pulsed mode at room temperature, with threshold currents as low as 394 mA.

High efficiency low threshold current 1.3 μm InAs quantum dot lasers on on-axis (001) GaP/Si September 27, 2017 High efficiency low threshold current 1.3 μm InAs quantum dot lasers on on-axis (001) GaP/Si

As a result of record low threading dislocation densities, the threshold current and threshold current density have gone down in our Quantum Dot lasers, and we see record high wallplug efficiencies for any laser on silicon.

1.3 μm submilliamp threshold quantum dot micro-lasers on Si August 1, 2017 Optica August 2017 cover

The cover of the latest issue of Optica shows the latest quantum dot microring lasers on silicon with record low lasing thresholds.  This is promising for next generation data center interconnects.

Looking for Postdocs (immediately) and Graduate Students for Admission in Fall 2018 July 1, 2017 Bowers Group 2017

We are looking for two photonics students and two postdocs for design, fabrication and testing of photonic integrated circuits. Students should apply to the ECE or Materials departments for Fall 2018 admission. Postdocs should apply directly to Prof. Bowers.

Semiconductor Today article on Quantum Dot Laser and Photodetector Integration June 30, 2017 Semiconductor Today

UCSB and HKUST demonstrated the integration of quantum dot lasers and photodetectors on silicon substrates. An ultra-low dark current of 0.8 nA and an internal responsivity of 0.9 A/W were measured in the O band.

Gordon Kino, 1928-2017 June 29, 2017 Gordon Kino

Gordon Kino was my PhD advisor and a great mentor and researcher.  He was my inspiration and model for a great professor. He will be missed by so many researchers across the world.

The Revolution Has Just Begun: Q&A with John Bowers January 8, 2017 Image of Dr. Bowers

UCSB successfully demonstrated an electrically pumped hybrid silicon laser a decade ago. That advance has paved the way for the commercial production of high-bandwidth silicon photonic devices. Today, Bowers is leading UC Santa Barbara’s Institute for Energy Efficiency’s involvement in the AIM initiative and is a central figure in this exciting field. Photonics Spectra spoke with Bowers about AIM, his breakthrough work and the impact of integrated photonics on medicine, communications and…

John Bowers awarded 2017 IEEE Photonics Award August 3, 2016 Image of Dr. Bowers and Dr. Komljenovic

John Bowers, Professor of Materials and of Electrical and Computer Engineering, has been awarded the 2017 IEEE Photonics Award in honor of his pioneering research in silicon photonics, including hybrid silicon lasers, photonic integrated circuits, and ultra low-loss waveguides.

Please click on the following link to read on. 

Best Chapter April 13, 2016 UCSB’s student chapter of IEEE’s Photonics Society, with faculty advisor John Bowers (top left)

The UC Santa Barbara student chapter of the Institute of Electrical and Electronics Engineer’s Photonics Society has been named Chapter of the Year for 2016.

Established four years ago, the student organization of young engineers at UCSB is recognized for its effort in promoting professional growth and career development in the field of photonics. “This international award exemplifies the strength of our local photonics community and the hard work of our members to promote…