Creating large Fock states and massively squeezed states in optics using systems with nonlinear bound states in the continuum

The quantization of the electromagnetic field leads directly to the existence of quantum mechanical states, called Fock states, with an exact integer number of photons. Despite these fundamental states being long-understood, and despite their many potential applications, generating them is largely an open problem. For example, at optical frequencies, it is challenging to deterministically generate Fock states of order two and beyond. Here, we predict the existence of a new effect in nonlinear optics, which enables the deterministic generation of large Fock states at arbitrary frequencies. The effect, which we call an n-photon bound state in the continuum, is one in which a photonic resonance (such as a cavity mode) becomes lossless when a precise number of photons n is inside the resonance. Based on analytical theory and numerical simulations, we show that these bound states enable a remarkable phenomenon in which a coherent state of light, when injected into a system supporting this bound state, can spontaneously evolve into a Fock state of a controllable photon number. This effect is also directly applicable for creating (highly) squeezed states of light, whose photon number fluctuations are (far) below the value expected from classical physics (i.e., shot noise). We suggest several examples of systems to experimentally realize the effects predicted here in nonlinear nanophotonic systems, showing examples of generating both optical Fock states with large n (n > 10), as well as more macroscopic photonic states with very large squeezing, with over 90% less noise (10 dB) than the classical value associated with shot noise

Fullwave Maxwell inverse design of axisymmetric, tunable, and multi-scale multi-wavelength metalenses

We demonstrate new axisymmetric inverse-design techniques that can solve problems radically different from traditional lenses, including \emph{reconfigurable} lenses (that shift a multi-frequency focal spot in response to refractive-index changes) and {\emph{widely separated}} multi-wavelength lenses ($\lambda = 1\,\mu$m and $10\,\mu$m). We also present experimental validation for an axisymmetric inverse-designed monochrome lens in the near-infrared fabricated via two-photon polymerization. Axisymmetry allows fullwave Maxwell solvers to be scaled up to structures hundreds or even thousands of wavelengths in diameter before requiring domain-decomposition approximations, while multilayer topology optimization with $\sim 10^5$ degrees of freedom can tackle challenging design problems even when restricted to axisymmetric structures.Comment: 13 pages, 6 figure

Biasing the quantum vacuum to control macroscopic probability distributions

One of the most important insights of quantum field theory is that electromagnetic fields must fluctuate. Even in the vacuum state, the electric and magnetic fields have a nonzero variance, leading to ubiquitous effects such as spontaneous emission, the Lamb shift, the Casimir effect, and more. These "vacuum fluctuations" have also been harnessed as a source of perfect randomness, for example to generate perfectly random photonic bits. Despite these achievements, many potential applications of quantum randomness in fields such as probabilistic computing rely on controllable probability distributions, which have not yet been realized on photonic platforms. In this work, we show that the injection of vacuum-level "bias" fields into a multi-stable optical system enables a controllable source of "biased" quantum randomness. We demonstrate this concept in an optical parametric oscillator (OPO). Ordinarily, an OPO initiated from the ground state develops a signal field in one of two degenerate phase states (0 and $\pi$) with equal probability. By injecting bias pulses which contain less than one photon on average, we control the probabilities associated with the two output states, leading to the first controllable photonic probabilistic bit (p-bit). We shed light on the physics behind this process, showing quantitative agreement between theory and experiment. Finally, we demonstrate the potential of our approach for sensing sub-photon level fields by showing that our system is sensitive to the temporal shape of bias field pulses far below the single photon level. Our results suggest a new platform for the study of stochastic quantum dynamics in nonlinear driven-dissipative systems, and point toward possible applications in ultrafast photonic probabilistic computing, as well as the sensing of extremely weak fields

USB-SPI translator

Objectives: The project involves the design of a communication interface between a computer and 37 serial interfaced D/A Converters to update their outputs and also process feedback information from the DACs outputs. Methods / Experiences / Results: A USB controller (FT245R) is used for the USB communication between the computer and the processing unit (ATmega88). The user is able to send the DACs update information toward the microcontroller which sends the digital values to the DACs. A CPLD device is used to select multiple channels of 37 DACs. The MCU can sample the DACs output voltage via its built-in A/D converter and then send the information to the computer in order to be displayed for the user. Two hardware boards are designed and fabricated. The main board, USB-SPI Translator which provides the power and data processing functions, is a general USB to SPI communication interface board. The other board is in charge of the DACs channels selection. After the realization of the hardware boards, firmware for the data processing unit (MCU) and the CPLD are written. Some experiments about the whole system demonstrate that the DACs are able to be updated individually with a desired voltage. The precision of the DACs outputs is about one decimal. The MCU can get a 10-bits digital value of the DACs output. The digitalized DACs outputs are transmitted to the computer and displayed for the user

Integrated Plasmonic Detectors and Mixers for Microwave and Terahertz Applications

In this dissertation, new integrated plasmonic electro-optic devices on a silicon photonics platform were developed for optical interconnects, microwave photonics and terahertz applications. Photodetectors compatible with the CMOS technology have shown great potential in implementing active silicon photonics circuits at infrared wavelengths. However, current technologies are facing fundamental bandwidth limitations. Here, we propose and experimentally demonstrate two plasmonic photodetectors operating at highest speed. First, a germanium-plasmonic waveguide photodetector simultaneously achieving beyond 100 GHz bandwidth, an internal quantum efficiency of 36% and low footprint. High-speed data reception at 72 Gbit/s is demonstrated. Such superior performance is attributed to the sub-wavelength confinement of the optical energy in a photoconductive based plasmonic-germanium waveguide detector enabling shortest drift paths for photo-generated carriers and a very small resistance-capacitance product. We show that combining plasmonic waveguides with an absorbing semiconductor enables efficient photodetection at highest operation speeds. Along the same line, graphene holds great promises for high-speed photodetection. Yet, the responsivity of graphene-based photodetectors is commonly limited by the weak absorption of the atomically thin structure. In the following, we propose and experimentally demonstrate a plasmonically enhanced waveguide-integrated graphene photodetector. The device, which combines a 6 um long monolayer of graphene with field-enhancing plasmonic structures, features at the same time a high external responsivity of 0.55 A/W and a fast photoresponse going beyond 110 GHz. The high efficiency and fast response of the device enables 100 Gbit/s PAM 2 and 100 Gbit/s PAM 4 data reception in an optical link experiment. Furthermore, microwave photonics and terahertz technologies are attracting a great interest due to a high demand for increased wireless capacity. To cope with the high bandwidth requirements, wireless carrier frequencies are shifting towards the millimeter-wave and terahertz bands. Nevertheless, optical fibers are carrying the global data traffic around the world. Ideally, future communication networks would offer full transparency and flexibility to switch between the optical and wireless domains. To this end, efficient, low-cost fiber-wireless transmitters and receivers are of crucial importance. In this work, we demonstrate for the first time a passive, all-optical, wireless-to-optical receiver in a transparent fiber-wireless-fiber link. We successfully transmit 20 Gbit/s over a wireless distance of 1 m and 10 Gbit/s over a 5 m distance at a carrier frequency of 60 GHz. This breakthrough has become possible by directly mapping the wireless information onto plasmonic signals by means of an antenna-coupled plasmonic modulator. By the direct wireless-to-optical mixing we can overcome any potential speed limitations associated with the electronics. Furthermore, the plasmonic scheme with its subwavelength feature and pronounced field confinement not only provides a built-in field enhancement of up to 90’000 over the incident field but also an ultra-compact design in a CMOS compatible structure. Finally, in the last decades terahertz waves that typically extend from the 100 GHz to the 10 THz frequency range enabled a large variety of new applications from astronomy to biology and medical sciences as well as information and communications technologies, among others. Still, most terahertz systems rely on bulky free-space optics. Their limited capabilities, high complexity and high cost strongly hinder the development of practical systems for a broader range of applications. Most prominently, chip-size high-performance terahertz sources and detectors would offer significant advantages in a multitude of areas. Here, we demonstrate a fiber-coupled, integrated plasmonic terahertz field detector on a silicon-photonics platform. The detector consists of two terahertz antenna-coupled plasmonic phase shifters integrated in a single on-chip Mach-Zehnder interferometer. The electro-optic phase shifters modulate the phase delay of a guided optical probe upon an incident oscillating terahertz field. The terahertz field amplitude is retrieved by a direct measurement of the probe power after the interferometer. The success of the scheme relies on the confinement of the terahertz field to a small volume of 10^(-8) (λ_THz/2)^3 in a plasmonic cavity and on the resonant enhancement of a dual-antenna design. The strong confinement and resonant approach also result in an extremely short interaction length of only 5 um, which eliminates the need for phase matching. We demonstrate an electro-optic bandwidth of 2.5 THz with a 65 dB dynamic range. The frequency response of the detector can be custom tailored by the terahertz antenna design, showing the flexibility of this technology and its potential for future low-cost, scalable and hand-held terahertz systems

Sub-micron Plasmonic Waveguide Resonator

An ultra-compact plasmonic resonator is experimentally demonstrated. The presented sub-gm long inline waveguide-coupled plasmonic resonator features a resonance around 1550 nm with a measured loaded quality factor of 20