We review the field of cavity optomechanics, which explores the interaction between electromagnetic radiation and nano- or micromechanical motion This review covers the basics of optical cavities and mechanical resonators, their mutual optomechanical interaction mediated by the radiation pressure force, the large variety of experimental systems which exhibit this interaction, optical measurements of mechanical motion, dynamical backaction amplification and cooling, nonlinear dynamics, multimode optomechanics, and proposals for future cavity quantum optomechanics experiments In addition, we describe the perspectives for fundamental quantum physics and for possible applications of optomechanical devices

Cavity Optomechanics

Artificial Neural Networks have dramatically improved performance for many machine learning tasks. We demonstrate a new architecture for a fully optical neural network that enables a computational speed enhancement of at least two orders of magnitude and three orders of magnitude in power efficiency over state-of-the-art electronics.

Deep learning with coherent nanophotonic circuits

Researchers use phase-change materials to demonstrate an integrated optical memory with 13.4 pJ switching energy.

Integrated all-photonic non-volatile multi-level memory

Silicon has long been established as the material of choice for the microelectronics industry. This is not yet true in photonics, where the limited degrees of freedom in material design combined with the indirect bandgap are a major constraint. Recent developments, especially those enabled by nanoscale engineering of the electronic and photonic properties, are starting to change the picture, and some silicon nanostructures now approach or even exceed the performance of equivalent direct-bandgap materials. Focusing on two application areas, namely communications and photovoltaics, we review recent progress in silicon nanocrystals, nanowires and photonic crystals as key examples of functional nanostructures. We assess the state of the art in each field and highlight the challenges that need to be overcome to make silicon a truly high-performing photonic material.

/pdf/silicon-nanostructures-for-photonics-and-photovoltaics-2usyvrhvg3.pdf

Silicon nanostructures for photonics and photovoltaics

We demonstrate the exceptionally-high third-order nonlinearity of integrated mono-layer graphene-silicon hybrid optoelectronics, enabling ultralow power resonant optical bistability, self-induced regenerative oscillations, and coherent four-wave mixing, all at few femto-joule cavity recirculating energies.

http://www.columbia.edu/cu/nanohv/papers/grapheneFWM_regenerationOscillations_GuWong_naturePhotonics2012.pdf

Regenerative oscillation and four-wave mixing in graphene optoelectronics

Although high-speed all-optical switches are expected to replace their electrical counterparts in information processing, their relatively large size and power consumption have remained obstacles. We use a combination of an ultrasmall photonic-crystal nanocavity and strong carrier-induced nonlinearity in InGaAsP to successfully demonstrate low-energy switching within a few tens of picoseconds. Switching energies with a contrast of 3 and 10 dB of 0.42 and 0.66 fJ, respectively, have been obtained, which are over two orders of magnitude lower than those of previously reported all-optical switches. The ultrasmall cavity substantially enhances the nonlinearity as well as the recovery speed, and the switching efficiency is maximized by a combination of two-photon absorption and linear absorption in the InGaAsP nanocavities. These switches, with their chip-scale integratability, may lead to the possibility of low-power, high-density, all-optical processing in a chip. All-optical switching energies as small as 0.42 fJ — two orders of magnitude lower than previously reported — are demonstrated in small photonic crystal cavities incorporating InGaAsP. These devices can switch within a few tens of picoseconds, and may therefore have potential for low-power high-density all-optical processing on a chip.

Sub-femtojoule all-optical switching using a photonic-crystal nanocavity

The ability to directly modulate a nanocavity laser with ultralow power consumption is essential for the realization of a CMOS-integrated, on-chip photonic network, as several thousand lasers must be integrated onto a single chip. Here, we show high-speed direct modulation (3-dB modulation bandwidth of 5.5 GHz) of an ultracompact InP/InGaAsP buried heterostructure photonic-crystal laser at room temperature by optical pumping. The required energy for transmitting one bit is estimated to be 13 fJ. We also achieve a threshold input power of 1.5 µW, which is the lowest observed value for room-temperature continuous-wave operation of any type of laser. The maximum single-mode fibre output power of 0.44 µW is the highest output power, to our knowledge, for photonic-crystal nanocavity lasers under room-temperature continuous-wave operation. Implementing a buried heterostructure leads to excellent device performance, reducing the active region temperature and effectively confining the carriers inside the cavity. Advanced on-chip photonic networks require integrated nanoscale lasers with low power consumption. Researchers have now demonstrated high-speed modulation of a compact heterostructure photonic crystal laser at room temperature with an unprecedented low required energy of ∼13 fJ per bit transmitted.

High-speed ultracompact buried heterostructure photonic-crystal laser with 13 fJ of energy consumed per bit transmitted

Large-scale densely integrated optical memory on a single photonic crystal chip is demonstrated. The wavelength-division-multiplexing (WDM) capabilities of nanophotonic memories are exploited for optical addressing. This work may enable optical random-access memories and a large-scale WDM photonic network-on-chip.

Large-scale integration of wavelength-addressable all-optical memories on a photonic crystal chip

Using photonic crystal cavities with a buried heterostructure design, scientists demonstrate all-optical RAM at power levels 300 times lower than previous attempts. The 30 nW devices could enable low-power large-scale optical RAM systems for handling high-bit-rate optical signals.

Ultralow-power all-optical RAM based on nanocavities

High-speed modulation and 4.4 fJ bit−1 data transmission is demonstrated using a photonic-crystal nanocavity laser. Its current threshold of 4.8 µA, modulation current efficiency of 2.0 GHz µA−0.5 and output power of 2.17 µW may enable on-chip photonic networks in combination with recently developed high-sensitivity receivers.

Tomonari Sato

Papers

Sub-femtojoule all-optical switching using a photonic-crystal nanocavity

High-speed ultracompact buried heterostructure photonic-crystal laser with 13 fJ of energy consumed per bit transmitted

Large-scale integration of wavelength-addressable all-optical memories on a photonic crystal chip

Ultralow-power all-optical RAM based on nanocavities

Few-fJ/bit data transmissions using directly modulated lambda-scale embedded active region photonic-crystal lasers