arXiv subjects

David R. Carlson

Publications and source records attributed to David R. Carlson.

At least 19 recordsLinked to original sources

arXiv2026

Integrated ytterbium gain for visible-near-infrared photonics

Rare-earth gain media form the foundation of modern optical communications, emerging quantum hardware, and ultrafast optics. While chip-scale integration can enable fiber-like, and potentially beyond-fiber, functionality with unprecedented scalability, development in the visible and near-infrared remains in its early stages. Here, we demonstrate ytterbium-based optical gain integrated into an aluminum oxide photonic platform, achieving both single-mode lasing and optical amplification in the near-infrared regime. This platform delivers optical amplification with output powers exceeding 0.5 W, an optical-to-optical conversion efficiency above 70%, and a noise figure of 3.3 dB, approaching the quantum limit for phase-insensitive amplification. Furthermore, we achieve femtosecond pulse amplification to a record peak power of 14 kW, enabling supercontinuum generation with visible dispersive waves extending from 780 to 476 nm in conjunction with nonlinear photonic devices. This platform is compatible with heterogeneous integration into standard photonic circuits, laying the foundation for scalable visible-near-infrared photonic systems, including coherent laser arrays, mode-locked lasers, optical clocks, and microwave oscillators.

physics.optics↗

arXiv2026

A scalable infrastructure for strontium optical clocks with integrated photonics

Optical atomic clocks provide exceptionally accurate and precise signals for timekeeping and precision measurements, but they require high-power, free-space laser configurations that limit scalability. We introduce and explore a scalable infrastructure for strontium (Sr) optical-lattice clocks that incorporates co-design of atomic-beam slowing and a magneto-optical trap (MOT) from an effusion source, generation of complex, three-dimensional free-space laser configurations with a photonic integrated circuit (PIC) and metasurface (MS) optics, and laser stabilization to a frequency-comb supercontinuum generated with integrated nonlinear photonics. With these elements, we realize MOTs of all stable strontium isotopes ($^{84}$Sr, $^{86}$Sr, $^{87}$Sr, $^{88}$Sr) with populations commensurate with natural abundances, demonstrating precise beam control and robustness. Access to laser-cooled alkaline-earth atoms with scalable integrated photonics enables system engineering for optical clocks, quantum sensing, and quantum information, and our experiments demonstrate extensible technologies that advance toward a Sr optical clock largely free of bulk optics.

physics.app-ph↗

arXiv2025

Monolithic 3D integration of tantalum pentoxide photonics on arbitrary substrates

The photonics landscape encompasses a wide scope of material platforms, each optimized for specific functionalities, yet no platform meets the demands of all current and evolving photonic applications. While combining integrated photonics materials enhances overall capability - such as unifying nonlinear optics, low-loss passive devices, and electro-optics - material and process compatibility remains a major challenge. We introduce full-wafer, monolithic 3D integration of tantalum pentoxide (Ta$_2$O$_5$, hereafter tantala) photonics onto arbitrary substrates, which we explore here with thin-film lithium niobate (LN) on silicon. Tantala's unique properties, importantly room-temperature deposition, low-temperature annealing, and low stress in thick films optimized for phase matching, make it well suited for monolithic 3D integration without compromising substrate performance or compatibility. We demonstrate low-loss, high-quality-factor microresonators and nanophotonics in tantala, robust quasi-phase-matching in poled LN waveguides, and efficient 3D interlayer routing. This enables us to demonstrate a rich palette of nonlinear frequency conversion processes, including $χ^{(3)}$ optical parametric oscillation (OPO) and soliton microcomb generation in tantala microresonators and photonic-crystal resonators, $χ^{(2)}$ second-harmonic generation (SHG) in periodically poled LN, and combinations thereof. Monolithic 3D integration with tantala opens a new paradigm for scalable, multifunctional photonic systems, enabling visible, near-IR, and nonlinear operation into existing photonic infrastructure.

physics.optics↗

arXiv2025

Amorphous metal oxide mixtures for high-Q integrated nonlinear photonics

Choice of material is ubiquitous in integrated photonics to design device properties, whereas changing material composition is much less common. With phase matching as an additional objective, constraints in depositing and patterning thin films limit the use of integrated nonlinear photonics to only select materials. Here, we explore an amorphous metal oxide mixture of titania (TiO2) and tantala (Ta2O5) in which material composition is a tool to enhance and customize photonics properties. In particular, the inclusion of titania reduces the oxygen-defect density in a tantala film, while maintaining a comparable Kerr nonlinear index. With ion-beam sputtering at room temperature, we deposit a thick, ultralow-loss titania-tantala film, and we nanopattern it to create microresonator frequency combs. Titania-tantala microresonators offer lower loss, higher index of refraction, and reduced optical absorption and photorefractive effects. Specifically, the titania-tantala mixture enables microresonator quality factor up to $10^7$ and a direct factor of 1.7 reduction in optical absorption. Our work demonstrates that composition in metal-oxide mixtures is a design parameter alongside the nanofabrication process and photonics design for integrated nonlinear photonics.

physics.optics↗

arXiv2025

Activating high-power parametric oscillation in photonic-crystal resonators

By engineering the mode spectrum of a Kerr microresonator, we selectively activate nonlinear phase matching amongst broadband parametric gain. At threshold, optical parametric oscillators (OPOs) emerge from vacuum fluctuations in the presence of a pump laser, and above threshold, OPOs seed the formation of intraresonator patterns and states, such as chaos and solitons. These competing nonlinear processes hinder an important application of OPOs as wavelength-variable, low-noise sources. Recently, nanopatterned microresonator OPOs have leveraged photonic crystal bandgaps to enable universal phase matching and control of nonlinear interactions. Here, we explore a design paradigm optimized for high-output power that uses geometric dispersion to suppress nonlinear interactions and a photonic crystal bandgap to activate only a single OPO interaction. Our devices convert an input pump laser to output signal and idler waves with powers exceeding 40 mW while maintaining spectral purity and side-mode suppression ratios greater than 40 dB. We show that this approach suits custom wavelengths by measuring four independent oscillators that vary only photonic crystal parameters to select output waves. Our experiments demonstrate that microresonators functionalized by photonic crystals offer a versatile and lossless palette of controls for nonlinear laser conversion.

physics.optics↗

arXiv2024

Propagation of pulsed light in an optical cavity in a gravitational field

All modern theories of gravitation, starting with Newton's, predict that gravity will affect the speed of light propagation. Einstein's theory of General Relativity famously predicted that the effect is twice the Newtonian value, a prediction that was verified during the 1919 solar eclipse. Recent theories of vector gravity can be interpreted to imply that gravity will have a different effect on pulsed light versus continuous-wave (CW) light propagating between the two mirrors of an optical cavity. Interestingly, we are not aware of any previous experiments to determine the relative effect of gravity on the propagation of pulsed versus CW light. In order to observe if there are small differences, we use a 6 GHz electro-optic frequency comb and low-noise CW laser to make careful measurements of the resonance frequencies of a high-finesse optical cavity. Once correcting for the effects of mirror dispersion, we determine that the cavity resonance frequencies for pulsed and CW light are the same to within our experimental error, which is on the order of $10^{-12}$ of the optical frequency, and one part in 700 of the expected gravitational shift.

physics.optics↗

arXiv2024

Nanophotonic oscillators for laser conversion beyond an octave

Many uses of lasers place the highest importance on access to specific wavelength bands. For example, mobilizing optical-atomic clocks for a leap in sensing requires compact lasers at frequencies spread across the visible and near infrared. Integrated photonics enables high-performance, scalable laser platforms, however, customizing laser-gain media to support wholly new bands is challenging and often prohibitively mismatched in scalability to early quantum-based sensing and information systems. Here, we demonstrate a microresonator optical-parametric oscillator (OPO) that converts a pump laser to an output wave within a frequency span exceeding an octave. We achieve phase matching for oscillation by nanopatterning the microresonator to open a photonic-crystal bandgap on the mode of the pump laser. By adjusting the nanophotonic pattern and hence the bandgap, the ratio of output OPO wave frequency span to required pump laser tuning is more than 10,000. We also demonstrate tuning the oscillator in free-spectral-range steps, more finely with temperature, and minimal additive frequency noise of the laser-conversion process. Our work shows that nanophotonics offers control of laser conversion in microresonators, bridging phase-matching of nonlinear optics and application requirements for laser designs.

physics.optics↗

arXiv2024

Laser-power consumption of soliton formation in a bidirectional Kerr resonator

Laser sources power extreme data transmission as well as computing acceleration, access to ultrahigh-speed signaling, and sensing for chemicals, distance, and pattern recognition. The ever-growing scale of these applications drives innovation in multi-wavelength lasers for massively parallel processing. We report a nanophotonic Kerr-resonator circuit that consumes the power of an input laser and generates a soliton frequency comb at approaching unit efficiency. By coupling forward and backward propagation, we realize a bidirectional Kerr resonator that supports universal phase matching but also opens excess loss by double-sided emission. Therefore, we induce reflection of the resonator's forward, external-coupling port to favor backward propagation, resulting in efficient, one-sided soliton formation. Coherent backscattering with nanophotonics provides the control to put arbitrary phase-matching and efficient laser-power consumption on equal footing in Kerr resonators. In the overcoupled-resonator regime, we measure 65% conversion efficiency of a 40 mW input pump laser, and the nonlinear circuit consumes 97% of the pump, generating the maximum possible comb power. Our work opens up high-efficiency soliton formation in integrated photonics, exploring how energy flows in nonlinear circuits and enabling laser sources for advanced transmission, computing, quantum sensing, and artificial-intelligence applications.

physics.optics↗

arXiv2023

Tailoring microcombs with inverse-designed, meta-dispersion microresonators

Nonlinear-wave mixing in optical microresonators offers new perspectives to generate compact optical-frequency microcombs, which enable an ever-growing number of applications. Microcombs exhibit a spectral profile that is primarily determined by their microresonator's dispersion; an example is the $ \operatorname{sech}^2 $ spectrum of dissipative Kerr solitons under anomalous group-velocity dispersion. Here, we introduce an inverse-design approach to spectrally shape microcombs, by optimizing an arbitrary meta-dispersion in a resonator. By incorporating the system's governing equation into a genetic algorithm, we are able to efficiently identify a dispersion profile that produces a microcomb closely matching a user-defined target spectrum, such as spectrally-flat combs or near-Gaussian pulses. We show a concrete implementation of these intricate optimized dispersion profiles, using selective bidirectional-mode hybridization in photonic-crystal resonators. Moreover, we fabricate and explore several microcomb generators with such flexible `meta' dispersion control. Their dispersion is not only controlled by the waveguide composing the resonator, but also by a corrugation inside the resonator, which geometrically controls the spectral distribution of the bidirectional coupling in the resonator. This approach provides programmable mode-by-mode frequency splitting and thus greatly increases the design space for controlling the nonlinear dynamics of optical states such as Kerr solitons.

physics.optics↗

arXiv2023

Threshold and laser-conversion in nanostructured-resonator parametric oscillators

We explore optical parametric oscillation (OPO) in nanophotonic resonators, enabling arbitrary, nonlinear phase-matching and nearly lossless control of energy conversion. Such pristine OPO laser converters are determined by nonlinear light-matter interactions, making them both technologically flexible and broadly reconfigurable. We utilize a nanostructured inner-wall modulation in the resonator to achieve universal phase-matching for OPO-laser conversion, but coherent backscattering also induces a counterpropagating pump laser. This depletes the intra-resonator optical power in either direction, increasing the OPO threshold power and limiting laser-conversion efficiency, the ratio of optical power in target signal and idler frequencies to the pump. We develop an analytical model of this system that emphasizes an understanding of optimal laser conversion and threshold behaviors, and we use the model to guide experiments with nanostructured-resonator OPO laser-conversion circuits, fully integrated on chip and unlimited by group-velocity dispersion. Our work demonstrates the fundamental connection between OPO laser-conversion efficiency and the resonator coupling rate, subject to the relative phase and power of counterpropagating pump fields. We achieve $(40\pm4)$ mW of on-chip power, corresponding to $(41\pm4)$% conversion efficiency, and discover a path toward near-unity OPO laser conversion efficiency.

physics.optics↗

arXiv2023

20 GHz fiber-integrated femtosecond pulse and supercontinuum generation with a resonant electro-optic frequency comb

Frequency combs with mode spacing in the range of 10 to 20 gigahertz (GHz) are critical for increasingly important applications such as astronomical spectrograph calibration, high-speed dual-comb spectroscopy, and low-noise microwave generation. While electro-optic modulators and microresonators can provide narrowband comb sources at this repetition rate, a significant remaining challenge is a means to produce pulses with sufficient peak power to initiate nonlinear supercontinuum generation spanning hundreds of terahertz (THz) as required for self-referencing in these applications. Here, we provide a simple, robust, and universal solution to this problem using off-the-shelf polarization-maintaining (PM) amplification and nonlinear fiber components. This fiber-integrated approach for nonlinear temporal compression and supercontinuum generation is demonstrated with a resonant electro-optic frequency comb at 1550 nm. We show how to readily achieve pulses shorter than 60 fs at a repetition rate of 20 GHz and with peak powers in excess of 2 kW. The same technique can be applied to picosecond pulses at 10 GHz to demonstrate temporal compression by a factor of 9x yielding 50 fs pulses with peak power of 5.5 kW. These compressed pulses enable flat supercontinuum generation spanning more than 600 nm after propagation through multi-segment dispersion-tailored anomalous-dispersion highly nonlinear fiber (HNLF) or tantala waveguides. The same 10 GHz source can readily achieve an octave-spanning spectrum for self-referencing in dispersion-engineered silicon nitride waveguides. This simple all-fiber approach to nonlinear spectral broadening fills a critical gap for transforming any narrowband 10 to 20 GHz frequency comb into a broadband spectrum for a wide range of applications that benefit from the high pulse rate and require access to the individual comb modes.

physics.optics↗

arXiv2022

Tunable lasers with optical-parametric oscillation in photonic-crystal resonators

By design access to laser wavelength, especially with integrated photonics, is critical to advance quantum sensors like optical clocks and quantum-information systems, and open opportunities in optical communication. Semiconductor-laser gain provides exemplary efficiency and integration but merely in developed wavelength bands. Alternatively, nonlinear optics requires control of phase matching, but the principle of nonlinear conversion of a pump laser to a designed wavelength is extensible. We report on laser-wavelength access by versatile customization of optical-parametric oscillation (OPO) with a photonic-crystal resonator (PhCR). By controlling the bandgap of a PhCR, we enable OPO generation across a wavelength range of 1234-2093 nm with a 1550 nm pump and 1016-1110 nm with a 1064 nm pump. Moreover, our tunable laser platform offers pump-to-sideband conversion efficiency of >10% and negligible additive optical-frequency noise across the output range. From laser design to simulation of nonlinear dynamics, we use a Lugiato-Lefever framework that predicts the system characteristics, including bi-directional OPO generation in the PhCR and conversion efficiency in agreement with our observations. Our experiments introduce tunable lasers by design with PhCR OPOs, providing critical functionalities in integrated photonics.

physics.optics↗

arXiv2021

Optical synthesis by spectral translation

Optical-frequency synthesizers are lasers stabilized and programmed from a microwave clock for applications, especially in fundamental measurements and spectroscopy, optical-communication links, and precision sensing of numerous physical effects. In a synthesizer, a frequency comb provides a reference grid across a broad spectrum and a frequency-tunable laser accomplishes synthesis by phase-lock to the comb. Optical synthesizers have matured to chip-scale with integrated photonics, however, the tunable laser and frequency comb fundamentally constrain the tuning range. Here, we present an optical synthesizer based on four-wave mixing (FWM) spectral translation of a tunable laser and a frequency comb. We implement both the spectral translation and the frequency comb by use of advanced microresonators. The intrinsic energy conservation of FWM ensures deterministic optical synthesis, and it allows a nearly arbitrary frequency tuning range by the dependence of resonant FWM on group-velocity dispersion, temperature, and tunable laser frequency. Moreover, we take advantage of highly efficient parametric amplification associated with spectral translation. We operate spectral translation across output ranges up to 200 THz, and we characterize it through ultraprecise optical-frequency metrology, demonstrating <0.1 Hz absolute accuracy and a fractional frequency precision of 4.7x10^(-13) in 1 s measurements. Our experiments introduce integrated-nonlinear-photonic circuits that enable complex intrinsic functionalities, such as our approach to optical-frequency synthesis with nearly limitless bandwidth.

physics.optics↗

arXiv2020

Group-velocity dispersion engineering of tantala integrated photonics

Designing integrated photonics, especially to leverage Kerr-nonlinear optics, requires accurate and precise knowledge of refractive index across the visible to infrared spectral ranges. Tantala (Ta_2O_5) is an emerging material platform for integrated photonics and nanophotonics that offers broadband ultralow loss, moderately high nonlinearity, and advantages for scalable and heterogeneous integration. We present refractive-index measurements on a thin film of tantala, and we explore the efficacy of this data for group-velocity dispersion (GVD) engineering with waveguide and ring-resonator devices. In particular, the observed spectral extent of supercontinuum generation in fabricated waveguides, and the wavelength dependence of free spectral range (FSR) in optical resonators provide a sensitive test of our integrated-photonics design process. Our work opens up new design possibilities with tantala, including with octave-spanning soliton microcombs.

physics.optics↗

arXiv2020

Tantala Kerr-nonlinear integrated photonics

Integrated photonics plays a central role in modern science and technology, enabling experiments from nonlinear science to quantum information, ultraprecise measurements and sensing, and advanced applications like data communication and signal processing. Optical materials with favorable properties are essential for nanofabrication of integrated-photonics devices. Here we describe a material for integrated nonlinear photonics, tantalum pentoxide (Ta$_2$O$_5$, hereafter tantala), which offers low intrinsic material stress, low optical loss, and efficient access to Kerr-nonlinear processes. We utilize >800-nm thick tantala films deposited via ion-beam sputtering on oxidized silicon wafers. The tantala films contain a low residual tensile stress of 38 MPa, and they offer a Kerr index $n_2$=6.2(23)$\times10^{-19}$ m$^2$/W, which is approximately a factor of three higher than silicon nitride. We fabricate integrated nonlinear resonators and waveguides without the cracking challenges that are prevalent in stoichiometric silicon nitride. The tantala resonators feature an optical quality factor up to $3.8\times10^6$, which enables us to generate ultrabroad-bandwidth Kerr-soliton frequency combs with low threshold power. Moreover, tantala waveguides enable supercontinuum generation across the near-infrared from low-energy, ultrafast seed pulses. Our work introduces a versatile material platform for integrated, low-loss nanophotonics that can be broadly applied and enable heterogeneous integration.

physics.optics↗

arXiv2019

Generating few-cycle pulses with integrated nonlinear photonics

Ultrashort laser pulses that last only a few optical cycles have been transformative tools for studying and manipulating light--matter interactions. Few-cycle pulses are typically produced from high-peak-power lasers, either directly from a laser oscillator, or through nonlinear effects in bulk or fiber materials. Now, an opportunity exists to explore the few-cycle regime with the emergence of fully integrated nonlinear photonics. Here, we experimentally and numerically demonstrate how lithographically patterned waveguides can be used to generate few-cycle laser pulses from an input seed pulse. Moreover, our work explores a design principle in which lithographically varying the group-velocity dispersion in a waveguide enables the creation of highly constant-intensity supercontinuum spectra across an octave of bandwidth. An integrated source of few-cycle pulses could broaden the range of applications for ultrafast light sources, including supporting new lab-on-a-chip systems in a scalable form factor.

physics.optics↗

arXiv2019

Stellar Spectroscopy in the Near-infrared with a Laser Frequency Comb

The discovery and characterization of exoplanets around nearby stars is driven by profound scientific questions about the uniqueness of Earth and our Solar System, and the conditions under which life could exist elsewhere in our Galaxy. Doppler spectroscopy, or the radial velocity (RV) technique, has been used extensively to identify hundreds of exoplanets, but with notable challenges in detecting terrestrial mass planets orbiting within habitable zones. We describe infrared RV spectroscopy at the 10 m Hobby-Eberly telescope that leverages a 30 GHz electro-optic laser frequency comb with nanophotonic supercontinuum to calibrate the Habitable Zone Planet Finder spectrograph. Demonstrated instrument precision <10 cm/s and stellar RVs approaching 1 m/s open the path to discovery and confirmation of habitable zone planets around M-dwarfs, the most ubiquitous type of stars in our Galaxy.

astro-ph.EP↗

arXiv2018

Dual-comb spectroscopy with tailored spectral broadening in Si$_3$N$_4$ nanophotonics

Si$_3$N$_4$ waveguides, pumped at 1550 nm, can provide spectrally smooth, broadband light for gas spectroscopy in the important 2 ${\mathrmμ}$m to 2.5 ${\mathrmμ}$m atmospheric water window, which is only partially accessible with silica-fiber based systems. By combining Er+:fiber frequency combs and supercontinuum generation in tailored Si$_3$N$_4$ waveguides, high signal-to-noise dual-comb spectroscopy (DCS) spanning 2 ${\mathrmμ}$m to 2.5 ${\mathrmμ}$m is demonstrated. Acquired broadband dual-comb spectra of CO and CO$_2$ agree well with database line shape models and have a spectral-signal-to-noise as high as 48$/\sqrt{\mathrm{s}}$, showing that the high coherence between the two combs is retained in the Si$_3$N$_4$ supercontinuum generation. The DCS figure of merit is 6$\times 10^6/\sqrt{\mathrm{s}}$, equivalent to that of all-fiber DCS systems in the 1.6 ${\mathrmμ}$m band. Based on these results, future DCS can combine fiber comb technology with Si$_3$N$_4$ waveguides to access new spectral windows in a robust non-laboratory platform.

physics.optics↗