David W. Grund

A single adiabatic microring-based laser in 220 nm silicon-on-insulator

We demonstrate a laser for the silicon photonics platform by hybrid integration with a III/V reflective semiconductor optical amplifier coupled to a 220 nm silicon-on-insulator half-cavity. We utilize a novel ultra-thin silicon edge coupler. A single adiabatic microring based inline reflector is used to select a lasing mode, as compared to the multiple rings and Bragg gratings used in many previous results. Despite the simplified design, the laser was measured to have on-chip 9.8 mW power, less than 220 KHz linewidth, over 45 dB side mode suppression ratio, less than -135 dB/Hz relative intensity noise, and 2.7% wall plug efficiency.

Integrated silicon-photonic module for generating widely tunable, narrow-line RF using injection-locked lasers

We have developed a system for generating widely tunable, narrow-line RF signals from a pair of injection-locked lasers. This system is based on injection seeding one laser with a selectable high-order sideband obtained from a second laser that is phase modulated by a narrow-line, low-frequency RF reference oscillator. When these coherent optical outputs are mixed on a fast photodiode, RF output is obtained, with linewidth and phase noise characteristics that are limited by the reference oscillator. The RF output can be tuned over a wide range, in multiples of the reference frequency, and can be fine-tuned by tuning the reference oscillator. In this paper, we present the results of our efforts to develop an integrated version of this system, based on a silicon-photonic integrated circuit coupled to III-V semiconductor gain chips. We describe the fabrication process of the integrated module using heterogeneous integration techniques, and present preliminary results including two lasers operating simultaneously on a single silicon-photonic chip.

Conformal Wideband Optically Addressed Transmitting Phased Array With Photonic Receiver

In this paper we present a wideband optically addressed transmitting phased array antenna, consisting of an ultra-wideband tunable RF synthesizer, an optical phase-feed network, and a high-speed photodetector-integrated conformal array antenna. RF source generation and the optical feed network are capable of covering a frequency range of up to 50 GHz. A conformal 4 × 4 Ka-band patch array antenna is designed, fabricated and characterized. The array is designed to sweep over ±40° from the broadside. An optically based detector is implemented to measure the far-field of the transmitting phased array. Embedded electronic control is developed for the RF synthesizer, optical feed network control, and photonic receiver. This system is consolidated into a portable cart for field testing. Extensive studies of the subsystems have been performed. Electrically controlled optical beam steering is demonstrated and characterized, and far-fields are measured, and compared with simulation results, showing excellent agreement.

Toward a widely tunable narrow linewidth RF source through heterogenous silicon photonic integration

By mixing two lasers together it, is possible to generate RF signals from near DC to hundreds of GHz. Through the use of a narrow-linewidth low-frequency oscillator, optical modulator, and injection locking, much higher frequency outputs can be produced that still retain the narrow linewidth of the low frequency oscillator. Here we focus on the design and implementation of an integrated device including photonic sources and modulators to realize the system described above. Specifically, we report on the creation and mixing of two tunable lasers on a silicon platform with a heterogeneously integrated gain medium realized in a III-V material system.

A Widely Tunable Narrow Linewidth RF Source Integrated in a Heterogeneous Photonic Module

Generating radio-frequency signals over the entire spectrum, from 1 to 100 GHz, typically requires the use of multiple oscillators designed only for specific narrow bands of operation within that spectrum. An optoelectronic system based on modulation side-band-injection-locked lasers is capable of generating RF frequencies tunable over a span of more than seven octaves with low phase noise . We present the results of our efforts to develop a heterogeneously integrated version of this system based on a silicon-photonic integrated circuit coupled to III-V semiconductor gain chips. Towards that end, we have successfully demonstrated an integrated laser module and achieved tunable RF generation with a ~ 1 Hz linewidth.

Heterogenous integrated silicon-photonic module for producing widely tunable narrow linewidth RF

Generating RF signals over the entire spectrum, from hundreds of MHz into the hundreds of GHz, has previously required the use of special oscillators designed only for specific bands of operation within that spectrum. An optoelectronic system based on side-band-injection-locked lasers is capable of generating RF frequencies tunable over a span of more than 7 octaves with extremely low phase noise. [1] Here we present the results of our efforts to develop a heterogeneously integrated version of this system based on a silicon-photonic integrated circuit coupled to III-V semiconductor gain chips. Towards that effort, we have successfully demonstrated an integrated module and shown tunable RF generation with a ~1 Hz linewidth.

Toward a widely tunable narrow linewidth RF source utilizing an integrated heterogenous silicon photonic module

A system for generating widely tunable, narrow-line RF signals from a pair of injection-locked lasers has been developed. By injection seeding one laser with a sideband obtained from a second laser that is phase modulated by a spectrally pure low-frequency RF reference oscillator and then mixing these coherent optical outputs on a fast photodiode, RF with the same linewidth and phase noise characteristics as the reference oscillator can be produced. By using harmonics of the reference oscillator the RF output can be tuned over a much wider range than the reference oscillator while maintaining its narrow linewidth.Here we present the results of our efforts to develop an integrated version of this system, based on a silicon-photonic integrated circuit coupled to III-V semiconductor gain chips.Towards that goal we have successfully demonstrated an integrated module and shown tunable RF generation with a 1 Hz linewidth.

Improved configuration and reduction of phase noise in a narrow linewidth ultrawideband optical RF source.

In this Letter, we report on the improved configuration of a widely tunable optical RF generation system, particularly for the generation of low-frequency RF, as well as the reduction of phase noise in that same system. Using an amplitude modulator, a simplified system design was demonstrated with fewer components and improved phase noise performance, especially at RF frequencies below ∼36 GHz. Excess phase noise due to acoustic vibrations of the optical fibers was also successfully eliminated by mechanical isolation. A minimum phase noise of -124 dBc/Hz at 10 kHz offset was demonstrated at 4 GHz.

Development of a widely tunable narrow linewidth RF generator using a hybrid silicon photonic platform

We have developed a system for generating widely tunable, narrow-line RF signals from a pair of injection-locked lasers. Here we focus on the design and implementation of an integrated module and analysis of the produced RF.

Toward an integrated silicon-photonic module for widely tunable narrow-line RF source using injection-locking

Through the use of a narrow-linewidth low-frequency oscillator, optical modulator, and injection locking, we have developed a system for generating widely tunable, narrow-line RF signals from a pair of injection-locked lasers. Here we focus on the design and implementation of an integrated device including photonic sources and modulators to realize the system described above. Specifically, we report on the creation and mixing of two tunable lasers on a silicon platform with a heterogeneously integrated gain medium realized in a III-V material system.