arXiv subjects

Baile Chen

Publications and source records attributed to Baile Chen.

16 recordsLinked to original sources

arXiv2025

All-optical control and multiplexed readout of multiple superconducting qubits

Superconducting quantum circuits operate at millikelvin temperatures, typically requiring independent microwave cables for each qubit for connecting room-temperature control and readout electronics. However, scaling to large-scale processors hosting hundreds of qubits faces a severe input/output (I/O) bottleneck, as the dense cable arrays impose prohibitive constraints on physical footprint, thermal load, wiring complexity, and cost. Here we demonstrate a complete optical I/O architecture for superconducting quantum circuits, in which all control and readout signals are transmitted exclusively via optical photons. Employing a broadband traveling-wave Brillouin microwave-to-optical transducer, we achieve simultaneous frequency-multiplexed optical readout of two qubits. Combined with fiber-integrated photodiode arrays for control signal delivery, this closed-loop optical I/O introduces no measurable degradation to qubit coherence times, with an optically driven single-qubit gate fidelity showing only a 0.19% reduction relative to standard microwave operation. These results establish optical interconnects as a viable path toward large-scale superconducting quantum processors, and open the possibility of networking multiple superconducting quantum computers housed in separate dilution refrigerators through a centralized room-temperature control infrastructure.

quant-ph↗

arXiv2025

Scalable Optical Links for Controlling Bosonic Quantum Processors

Superconducting quantum computing has the potential to revolutionize computational capabilities. However, scaling up large quantum processors is limited by the cumbersome and heat-conductive electronic cables that connect room-temperature control electronics to quantum processors, leading to significant signal attenuation. Optical fibers provide a promising solution, but their use has been restricted to controlling simple two-level quantum systems over short distances. Here, we demonstrate optical control of a bosonic quantum processor, achieving universal operations on the joint Hilbert space of a transmon qubit and a storage cavity. Using an array of cryogenic fiber-integrated uni-traveling-carrier photodiodes, we prepare Fock states containing up to ten photons. Additionally, remote control of bosonic modes over a transmission distance of 15 km has been achieved, with fidelities exceeding 95%. The combination of high-dimensional quantum control, multi-channel operation, and long-distance transmission addresses the key requirements for scaling superconducting quantum computers and enables architectures for distributed quantum data centers.

quant-ph↗

arXiv2025

Integrated thin film lithium niobate mid-infrared modulator

The mid-infrared spectral range holds great promise for applications such as molecular spectroscopy and telecommunications. Many key molecules exhibit strong absorption features in this range, and free-space optical communication benefits from reduced atmospheric attenuation and low transmission losses in specific wavelength bands spanning from 3 to 14 $\mu m$. Recent progress in MIR photonics has been fuelled by the rapid development of efficient light sources and detectors. However, further advancement is hindered by the lack of low-loss, high-performance integrated photonic platforms and modulators. Lithium niobate on sapphire is a promising candidate, operating across a broad spectral range from 0.4 $\mu m$ to 4.5 $\mu m$. We demonstrate a broadband, high-speed lithium niobate on sapphire Mach-Zehnder electro-optic modulator operating from 3.95 to 4.3 $\mu m$. The device achieves a 3 dB bandwidth exceeding 20 GHz, an extinction ratio of 34 dB, and a half-wave voltage of 22 V$\cdot$cm, delivering optical output power at the half-milliwatt level. These properties are leveraged to demonstrate data transmission at 10 Gbit/s. The modulator is also used to generate a frequency comb with a width of 80 GHz. Furthermore, we demonstrate full $\pi$-phase modulation in the MIR, representing a key milestone for integrated MIR photonics. These results establish a pathway toward high-speed, energy-efficient MIR photonic systems for applications in telecommunications, sensing, and quantum technologies.

physics.optics↗

arXiv2025

A chip-based optoelectronic-oscillator frequency comb

Microresonator-based Kerr frequency combs ("Kerr microcombs") constitute chip-scale frequency combs of broad spectral bandwidth and repetition rate ranging from gigahertz to terahertz. An appealing application exploiting microcombs' coherence and large repetition rate is microwave and millimeter-wave generation. Latest endeavor applying two-point optical frequency division (OFD) on photonic-chip-based microcombs has created microwaves with exceptionally low phase noise. Nevertheless, microcomb-based OFD still requires extensive active locking, additional lasers, and external RF or microwave sources, as well as sophisticated initiation. Here we demonstrate a simple and entirely passive (no active locking) architecture, which incorporates an optoelectronic oscillator (OEO) and symphonizes a coherent microcomb and a low-noise microwave spontaneously. Our OEO microcomb leverages state-of-the-art integrated chip devices including a high-power DFB laser, a broadband silicon Mach-Zehnder modulator, an ultralow-loss silicon nitride microresonator, and a high-speed photodetector. Each can be manufactured in large volume with low cost and high yield using established CMOS and III-V foundries. Our system synergizes a microcomb of 10.7 GHz repetition rate and an X-band microwave with phase noise of $-$97/$-$126/$-$130 dBc/Hz at 1/10/100 kHz Fourier frequency offset, yet does not demand active locking, additional lasers, and external RF or microwave sources. With potential to be fully integrated, our OEO microcomb can become an invaluable technology and building block for microwave photonics, radio-over-fiber, and optical communication.

physics.optics↗

arXiv2025

Modified uni-travelling-carrier photodiodes with 206 GHz bandwidth and 0.81 A/W external responsivity

The accelerating demand for wireless communication necessitates wideband, energy-efficient photonic sub-terahertz (sub-THz) sources to enable ultra-fast data transfer. However, as critical components for THz photonic mixing, photodiodes (PDs) face a fundamental trade-off between quantum efficiency and bandwidth, presenting a major obstacle to achieving high-speed performance with high optoelectronic conversion efficiency. Here, we overcome this challenge by demonstrating an InP-based, waveguide-integrated modified uni-traveling carrier photodiode (MUTC-PD) with bandwidth exceeding 200 GHz and a bandwidth-efficiency product (BEP) surpassing 130 GHz. Incorporating a spot-size converter (SSC) together with optimized electric-field distribution, balanced carrier transport, and minimized parasitic capacitance, the device achieves a 3-dB bandwidth of 206 GHz and an external responsivity of 0.81 A/W, setting a new BEP benchmark. Packaged with WR-5.1 waveguide output, it delivers radio-frequency (RF) power exceeding -5 dBm across the 127-185 GHz frequency range. As a proof of concept, we achieved a wireless transmission of 54 meters with a single-line rate of up to 120 Gbps, leveraging photonics-aided technology without requiring a low-noise amplifier (LNA). This work establishes a pathway to significantly enhance optical power budgets and reduce energy consumption, presenting a transformative step toward high-bandwidth, high-efficiency sub-THz communication systems and next-generation wireless networks.

physics.app-ph↗

arXiv2024

On-chip Brillouin Amplifier in Suspended Lithium Niobate Nanowaveguides

Thin film lithium niobate (TFLN) has emerged as a leading material platform for integrated nonlinear photonics, enabling transformative applications such as broadband Kerr soliton microcomb and high-speed electro-optic modulation. While stimulated Brillouin scattering has been numerically proposed in TFLN, achieving sufficient gain remains challenging due to the requirement for the simultaneous low optical and mechanical losses of the device. In this work, we systematically characterize the angle-dependence of Brillouin gain coefficients in x-cut membrane-suspended TFLN nanowaveguides, taking into account the anisotropy of the photoelastic coefficients in lithium niobate. We report a Brillouin gain coefficient of 129.5 m$^{-1}$W$^{-1}$ and further demonstrate the Brillouin frequency tuning through variations in either pump frequency or chip operating temperature. Based on the suspended TFLN nanowaveguide, by optimizing the confinement of both photonic and phononic modes, we have achieved a Brillouin amplifier with a record-high gain of 8.5 dB. This result not only validates the feasibility of strong guided Brillouin interaction using suspended TFLN nanowaveguides, but also paves the way for novel on-chip sensing and signal processing applications.

physics.optics↗

arXiv2024

A chip-integrated comb-based microwave oscillator

Low-noise microwave oscillators are cornerstones for wireless communication, radar and clocks. Optical frequency combs have enabled photonic microwaves with unrivalled noise performance and bandwidth. Emerging interest is to generate microwaves using chip-based frequency combs, namely microcombs. Here, we demonstrate the first, fully integrated, microcomb-based, microwave oscillator chip. The chip, powered by a microelectronic circuit, leverages hybrid integration of a DFB laser, a nonlinear microresonator, and a high-speed photodetector. Each component represents the best of its own class, yet allows large-volume manufacturing with low cost in CMOS foundries. The hybrid chip outputs an ultralow-noise laser of 6.9 Hz linewidth, a microcomb of 10.7 GHz repetition rate, and a 10.7 GHz microwave of 6.3 mHz linewidth -- all three in one entity of 76 mm$^2$ size.The microwave phase noise reaches -75/-105/-130 dBc/Hz at 1/10/100 kHz Fourier offset frequency. Our results can reinvigorate our information society for communication, sensing, timing and precision measurement.

physics.optics↗

arXiv2024

Ultra-fast Waveguide MUTC Photodiodes over 220 GHz

We present InP-based evanescently-coupled waveguide modified uni-traveling carrier photodiodes (MUTC-PDs) exhibiting a breakthrough in bandwidth. The optimization of carrier transport and optical coupling is achieved through a detailed discussion on the design of the cliff layer and waveguide layer. Addressing the parasitic capacitance challenge, we introduce benzocyclobutene (BCB) beneath the PD electrodes, effectively overcoming the bandwidth bottleneck associated with the RC time constant. Devices with sizes of 2 * 7 um2 and 2 * 10 um2 achieve 3-dB bandwidths over 220 GHz, along with external responsivities of 0.161 A/W and 0.237 A/W, respectively. Notably, the RF output power reaches a peak of -1.69 dBm at 215 GHz for 2 * 15 um2 PDs.

physics.app-ph↗

arXiv2023

Single-pixel p-graded-n junction spectrometers

Ultra-compact spectrometers are becoming increasingly popular for their promising applications in biomedical analysis, environmental monitoring, and food safety. In this work, we report a novel single-pixel-photodetector spectrometer with a spectral range from 480 nm to 820 nm, based on the AlGaAs/GaAs p-graded-n junction with a voltage-tunable optical response. To reconstruct the optical spectrum, we propose a tailored method called Neural Spectral Fields (NSF) that leverages the unique wavelength and bias-dependent responsivity matrix. Our spectrometer achieves a high spectral wavelength accuracy of up to 0.30 nm and a spectral resolution of up to 10 nm. Additionally, we demonstrate the high spectral imaging performance of the device. The compatibility of our demonstration with the standard III-V process greatly accelerates the commercialization of miniaturized spectrometers.

physics.app-ph↗

arXiv2020

High-speed InAs/GaSb Mid-Wave Infrared Interband Cascade Photodetector at Room Temperature

High speed mid-wave infrared (MWIR) photodetectors have important applications in the emerging areas such high-precision frequency comb spectroscopy and light detection and ranging (LIDAR). In this work, we report a high-speed room-temperature mid-wave infrared interband cascade photodetector (ICIP) based on a type-II InAs/GaSb superlattice. The devices show an optical cut-off wavelength around 5um and a 3-dB bandwidth up to 7.04 GHz. The relatively low dark current density around 9.39 x 10-2 A/cm2 under -0.1 V is also demonstrated at 300 K. These results validate the advantages of ICIPs to achieve both high-frequency operation and low noise at room temperature. Limitations on the high-speed performance of the detector are also discussed based on the S-parameter analysis and other RF performance measurement.

physics.app-ph↗

arXiv2020

High Speed Mid-Wave Infrared Uni-traveling Carrier Photodetector

Mid-wave infrared (MWIR) frequency comb is expected to dramatically improve the precision and sensitivity of molecular spectroscopy. For high resolution application, high speed MWIR photodetector is one of the key components, however, the commercially available high speed MWIR photodetector only has sub-GHz bandwidth currently. In this paper, we demonstrate, for the first time to our knowledge, a high speed mid-wave infrared (MWIR) uni-traveling carrier photodetector based on InAs/GaSb type-II superlattice (T2SL) at room temperature. The device exhibits a cutoff wavelength of 5.6μm, and 3dB bandwidth of 6.58 GHz for a 20μm diameter device at 300K. These promising results show the device has potential to be utilized in high speed applications such as frequency comb spectroscopy, free space communication and others. The limitations on the high frequency performance of the photodetectors are also discussed.

physics.app-ph↗

arXiv2019

High Speed Mid-Infrared Interband Cascade Photodetector Based on InAs/GaSb Type-II Superlattice

High speed mid-wave infrared (MWIR) photodetectors have applications in the areas such as free space optical communication and frequency comb spectroscopy. However, most of the research on the MWIR photodetectors is focused on how to increase the quantum efficiency and reduce the dark current, in order to improve the detectivity (D*), and the 3dB bandwidth performance of the corresponding MWIR photodetectors is still not fully studied. In this work, we report and characterize a MWIR interband cascade photodetector based on InAs/GaSb type-II superlattice with a 50% cutoff wavelength at ~5.3 um at 300 K. The 3 dB cutoff frequency is 2.4 GHz at 300 K, for a 40 μm circular diameter device under -5 V applied bias. Limitations on the detector high speed performance are also discussed.High speed mid-wave infrared (MWIR) photodetectors have applications in the areas such as free space optical communication and frequency comb spectroscopy. However, most of the research on the MWIR photodetectors is focused on how to increase the quantum efficiency and reduce the dark current, in order to improve the detectivity (D*), and the 3dB bandwidth performance of the corresponding MWIR photodetectors is still not fully studied. In this work, we report and characterize a MWIR interband cascade photodetector based on InAs/GaSb type-II superlattice with a 50% cutoff wavelength at ~5.3 um at 300 K. The 3 dB cutoff frequency is 2.4 GHz at 300 K, for a 40 um circular diameter device under -5 V applied bias. Limitations on the detector high speed performance are also discussed.

physics.app-ph↗

arXiv2019

Demonstration of Si based InAs/GaSb type-II superlattice p-i-n photodetector

In this paper, mid-wave infrared photodetection based on an InAs/GaSb type-II superlattice p-i-n photodetector grown directly on Si substrate is demonstrated and characterized. Excitation power dependence on integrated intensity from the photoluminescence measurements reveals a power coefficient of P~I0.74, indicating that defects related process is playing an important role in the predominant recombination channel for photogenerated carriers. At 70 K, the device exhibits a dark current density of 2.3 A/cm2 under -0.1 V bias. Arrhenius analysis of dark current shows activation energies much less than half of the active layer bandgap, which suggests that the device is mainly limited by surface leakage and defect-assisted tunneling, consistent with the photoluminescence analysis. The detector shows 50% cutoff wavelength at ~5.5 um at 70 K under bias of -0.1 V. The corresponding peak responsivity and specific detectivity are 1.2 A/W and 1.3*10e9 cm*Hz1/2/W, respectively. Based on these optoelectronics characterization results, reduction of defects by optimizing the III/V-Si interface, and suppression of surface leakage channels are argued to be the main factors for performance improvement in this Si-based T2SL detector towards low cost, large-format MWIR detection system on Si photonics platform.

physics.app-ph↗

arXiv2019

Deep levels analysis in wavelength extended InGaAsBi photodetector

InP based dilute Bismide InGaAsBi material is emerging as a promising candidate for extending short wavelength infrared detection. One critical factor to limit the performance of these InGaAsBi photodiodes is dark current caused by defects within the material. In this work, low frequency noise spectroscopy (LFNS) and temperature varied photoluminescence was used to characterize the defect levels in the devices. Three deep levels located at Ec -0.33 eV, Ev +0.14 eV, and Ec -0.51 eV were identified from the LFNS spectra, which are consistent with emission peak energy found by photoluminescence spectra of InGaAsBi.

physics.app-ph↗

arXiv2019

InGaAsP/InP uni-travelling-carrier photodiode at 1064nm wavelength

High-speed back-illuminated uni-traveling-carrier photodiodes at 1064nm were demonstrated grown on InP with 3dB bandwidth of 17.8 GHz at -5 V bias, using InGaAsP as absorption layer. PDs with 40um diameter deliver RF output power levels as high as 19.5 dBm at 13 GHz. This structure can achieve low dark current density of 10 nA per cm2 at -5V bias and quantum efficiency of 45.2% at 1064nm. An analytical model based on S-parameter fitting was built to extract parameter to access the bandwidth limiting factors.

physics.app-ph↗

arXiv2019

Two-micron wavelength high speed photodiode with InGaAs/GaAsSb type-II multiple quantum wells absorber

Current optical communication system operating at 1.55 μm wavelength band may not be able to continually satisfy the growing demand on the data capacity within the next few years. Opening a new spectral window at around 2 μm wavelength with recently developed hollow-core photonic band gap fiber and thulium-doped fiber amplifier is a promising solution to increase the transmission capacity due to the low loss and wide bandwidth properties of these components at this wavelength. However, as a key component, the already demonstrated high speed photodetectors at 2 μm wavelength are still not comparable with those at 1.55 μm wavelength band, which chokes the feasibility of the new spectral window. In this work, we, for the first time, demonstrated a high speed uni-traveling carrier photodiode for 2 μm applications with InGaAs/GaAsSb type-II multiple quantum wells as the absorption region, which is lattice matched to InP. The device shows a 3dB bandwidth of 25 GHz at -3 V bias voltage and is, to the best of our knowledge, the fastest photodiodes among all group III-V and group IV photodetectors working in 2 μm wavelength range.

physics.app-ph↗