Photonic integrated circuit comprising a whistle-geometry ring laser, injecting waveguide, distributed-Bragg reflector master laser, outcoupling waveguides, and a monitoring ring photodetector has been fabricated and characterized.

We report on the use of etching and regrowth to shift the longitudinal resonance wavelength of adjacent VCSELs by -4nm from 980nm. The etched VCSEL exhibited less than 5% change in threshold (from 0.36mA) and slope efficiency relative to neighboring un-etched VCSELs. This etch and regrowth technique can be applied to produce wavelength-division multiplexed (WDM) VCSEL arrays with close spacing (<100microns). We will also discuss applications to 2-dimensional index engineering of novel VCSEL devices, since wavelength shifting is equivalent to effective index tuning.

Piezoelectric acoustic devices that are integrated with semiconductors can leverage the acoustoelectric effect, allowing functionalities such as gain and isolation to be achieved in the acoustic domain. This could lead to performance improvements and miniaturization of radio-frequency electronic systems. However, acoustoelectric amplifiers that offer a large acoustic gain with low power consumption and noise figure at microwave frequencies in continuous operation have not yet been developed. Here we report non-reciprocal acoustoelectric amplifiers that are based on a three-layer heterostructure consisting of an indium gallium arsenide (In 0.53 Ga 0.47 As) semiconducting film, a lithium niobate (LiNbO 3 ) piezoelectric film, and a silicon substrate. The heterostructure can continuously generate 28.0 dB of acoustic gain (4.0 dB net radio-frequency gain) for 1 GHz phonons with an acoustic noise figure of 2.8 dB, while dissipating 40.5 mW of d.c. power. We also create a device with an acoustic gain of 37.0 dB (11.3 dB net gain) at 1 GHz with 19.6 mW of d.c. power dissipation and a non-reciprocal transmission of over 55 dB.

We have fabricated 3D printed micro-optics to feedback light into an 850-nm VCSEL with reduced top-mirror reflectivity and control its transverse modes. Our goal is to create a single-frequency VCSEL with output power on the order of 10 mW for use in atomic and quantum physics. Feedback of 50% can reduce threshold current 5-fold and preferentially select the fundamental transverse mode. We will compare theory and experiment for micro-optic length scales near 100 microns, yielding Gaussian mode diameters near 10 microns.

This work presents a 3-Port acoustoelectric switch design for surface acoustic wave signal processing. Using a multistrip coupler, the input acoustic wave at Port 1 is split into two parallel and electrically cross-linked acoustoelectric delay lines where an applied voltage can alter the gain and attenuation in each delay line based on the voltage polarity. The switch is demonstrated using a 270 MHz Leaky SAW mode on an InGaAs on 41° Y-cut lithium niobate heterostructure. Applying a +40 V voltage pulse results in an IL of -12.5 dB and -57.5 dB in the gain and isolation switch paths, respectively. This leads to a 45 dB difference in signal strength at the output ports.

We present progress on the synthesis of semimetal Cd3As2 by metal-organic chemical-vapor deposition (MOCVD). Specifically, we have optimized the growth conditions needed to obtain technologically useful growth rates and acceptable thin-film microstructures, with our studies evaluating the effects of varying the temperature, pressure, and carrier-gas type for MOCVD of Cd3As2 when performed using dimethylcadmium and tertiarybutylarsine precursors. In the course of the optimization studies, exploratory Cd3As2 growths are attempted on GaSb substrates, strain-relaxed InAs buffer layers grown on GaSb substrates, and InAs substrates. Notably, only the InAs-terminated substrate surfaces yield desirable results. Extensive microstructural studies of Cd3As2 thin films on InAs are performed by using multiple advanced imaging microscopies and x-ray diffraction modalities. The studied films are 5-75 nm in thickness and consist of oriented, coalesced polycrystals with lateral domain widths of 30-80 nm. The most optimized films are smooth and specular, exhibiting a surface roughness as low as 1.0 nm rms. Under cross-sectional imaging, the Cd3As2-InAs heteminterface appears smooth and abrupt at a lower film thickness, similar to 30 nm, but becomes quite irregular as the average thickness increases to similar to 55 nm. The films are strain-relaxed with a residual biaxial tensile strain (epsilon(xx) = +0.0010) that opposes the initially compressive lattice-mismatch strain of Cd3As2 coherent on InAs (epsilon(xx) = -0.042). Importantly, phase-identification studies find a thin-film crystal structure consistent with the P4(2)/nbc space group, placing MOCVD-grown Cd3As2 among the Dirac semimetals of substantial interest for topological quantum materials studies.

The addition of active, nonlinear, and nonreciprocal functionalities to passive piezoelectric acoustic wave technologies could enable all-acoustic and therefore ultra-compact radiofrequency signal processors. Toward this goal, we present a heterogeneously integrated acoustoelectric material platform consisting of a 50 nm indium gallium arsenide epitaxial semiconductor film in direct contact with a 41° YX lithium niobate piezoelectric substrate. We then demonstrate three of the main components of an all-acoustic radiofrequency signal processor: passive delay line filters, amplifiers, and circulators. Heterogeneous integration allows for simultaneous, independent optimization of the piezoelectric-acoustic and electronic properties, leading to the highest performing surface acoustic wave amplifiers ever developed in terms of gain per unit length and DC power dissipation, as well as the first-ever demonstrated acoustoelectric circulator with an isolation of 46 dB with a pulsed DC bias. Finally, we describe how the remaining components of an all-acoustic radiofrequency signal processor are an extension of this work.

InAs are performed by using multiple advanced imaging microscopies and x-ray diffraction modalities. The studied films are 5–75 nm in thickness and consist of oriented, coalesced polycrystals with lateral domain widths of 30–80 nm. The most optimized films are smooth and specular, exhibiting a surface roughness as low as 1.0 nm rms. Under cross-sectional imaging, the Cd3As2-InAs heterointerface appears smooth and abrupt at a lower film thickness, ~30 nm, but becomes quite irregular as the average thickness increases to ~55 nm. The films are strain-relaxed with a residual biaxial tensile strain (ϵxx = +0.0010) that opposes the initially compressive lattice-mismatch strain of Cd3As2 coherent on InAs (ϵxx = - 0.042). Importantly, phase-identification studies find a thin-film crystal structure consistent with the P42/nbc space group, placing MOCVD-grown Cd3As2 among the Dirac semimetals of substantial interest for topological quantum materials studies.

This paper demonstrates a monolithic surface acoustic wave amplifier fabricated by state-of-the-art heterogenous integration of a III-V InGaAs-based epitaxial material stack and LiNbO3. We compare amplification of Raleigh-SAW and leaky-SAW modes on a on Y-cut, X-propagating delay line amplifier. Due to the superior properties of the materials employed, we observe a net terminal gain of 3dB for an LSAW overtone mode This platform enables further advances in active and non-reciprocal piezoelectric acoustic devices.

Heterogeneous Integration (HI) may enable optoelectronic transceivers for short-range and long-range radio frequency (RF) photonic interconnect using wavelength-division multiplexing (WDM) to aggregate RF signals, provide galvanic isolation, and reduce crosstalk and interference. Integration of silicon Complementary Metal-Oxide-Semiconductor (CMOS) electronics with InGaAsP compound semiconductor photonics provides the potential for high-performance microsystems that combine complex electronic functions with optoelectronic capabilities from rich bandgap engineering opportunities, and intimate integration allows short interconnects for lower power and latency. The dominant pure-play foundry model plus the differences in materials and processes between these technologies dictate separate fabrication of the devices followed by integration of individual die, presenting unique challenges in die preparation, metallization, and bumping, especially as interconnect densities increase. In this paper, we will describe progress towards realizing an S-band WDM RF photonic link combining 180 nm silicon CMOS electronics with InGaAsP integrated optoelectronics, using HI processes and approaches that scale into microwave and millimeter-wave frequencies.

We experimentally observe frequency conversion via electromagnetic wave interaction with a high quality-factor resonance in an array of resonators whose refractive indices are varied on an ultrafast timescale. Further, we describe the observations using coupled-mode-theory.

We report on the design and characterization of multi-mirror vertical-cavity surface-emitting lasers (VCSELs) that achieve linewidths less than 2 MHz. We have fabricated all-semiconductor multi-mirror VCSELs at 850 nm that operate in a single mode and are suitable for high-resolution spectroscopy. Cold-cavity linewidth measurements confirm increased quality factors relative to standard VCSEL resonators. Frequency noise power spectral density measurements exhibit 1/f noise and white-noise floors consistent with Lorentzian linewidths less than 2 MHz.

This paper demonstrates a monolithic surface acoustic wave amplifier fabricated by state-of-the-art heterogenous integration of a III-V InGaAs-based epitaxial material stack and LiNbO3. Due to the superior properties of the materials employed, we observe electron gain and also non-reciprocal gain in excess of 30dB with reduced power consumption. Additionally, we present a framework for performance optimization as a function of material parameters for a targeted gain. This platform enables further advances in active and non-reciprocal piezoelectric acoustic devices.

We demonstrate ultrafast tuning of Fano resonances in a broken symmetry III-V metasurface using optical pumping. The resonance is spectrally shifted by 10 nm under low pump fluences of < 100 uJ.cm−2. © 2019 The Author(s)