Photonic Crystal Nanocavity Laser Research Articles

Photonic crystal nanolasers in polydimethylsiloxane thin film for sensing quantities leading to strain

We propose and realize a 1D photonic crystal nanocavity laser embedded in a polydimethylsiloxane (PDMS) thin film. The nanolaser in PDMS exhibits a significant optical response to structural deformation. It can be attached to object surfaces or integrated into different configurations, enabling the detection of different quantities that induce strain in the film. In experiments, this nanolaser can detect temperature variations or micrometer-scale bending degrees by attaching it to a temperature-controllable or bendable plate, respectively. Moreover, we further utilize the film as a diaphragm of a chamber to demonstrate its potential as a highly sensitive pressure gauge and chemical sensor. By adjusting the thickness of the PDMS thin film and the position of the nanolaser, we experimentally achieved a minimum detectable gas pressure variation of 0.12 kPa and a sensing dynamic range of 46 dB. We also investigate the optical response of the nanolaser to the swelling of the PDMS thin film induced by different organic solvents in experiments. The experimental wavelength shift rates over time are proportional to different chemical vapors’ PDMS swelling ratios, which can be used to identify specific chemical vapors within the chamber that induce PDMS swelling. Based on the experimental results and the capability of reattaching to different objects or configurations, we believe that our PhC nanolaser demonstrated herein holds significant potential as a highly sensitive mechanical and chemical sensor.

Electrically‐Driven Photonic Crystal Lasers with Ultra‐low Threshold

AbstractLight sources with ultra‐low energy consumption and high performance are required to realize optical interconnects for on‐chip communication. Photonic crystal (PhC) nanocavity lasers are one of the most promising candidates for this role. In this work, a continuous‐wave PhC nanolaser with an ultra‐low threshold current of 10.2 µA emitting at 1540 nm and operated at room temperature is demonstrated. The lasers are InP‐based bonded on silicon (Si), and comprise a buried heterostructure active region and lateral p–i–n junction, feature CMOS‐compatible drive voltage, and exhibit low self‐heating. Carrier leakage is a fundamental limitation of the lateral pumping scheme that is identified as unwanted spontaneous emission from the InP p–i interface, limiting the injection efficiency to 3% which further decreases at higher current. The effect of fabrication disorder and p‐doping absorption on the Q‐factor is studied experimentally showing that p‐doping limits the Q‐factor to 8000, with a p‐doping absorption coefficient of 120 cm−1.

Static and Dynamic Analysis of Lasing Action from Single and Coupled Photonic Crystal Nanocavity Lasers**Supported by the National Key Basic Research Special Fund/CNKBRSF of China under Grant Nos 2012CB933501, 2016YFA0301102, 2016YFB0401804 and 2016YFB0402203, the National Natural Science Foundation of China under Grant Nos 61535013, 61321063 and 61137003, the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant

The single and coupled photonic crystal nanocavity lasers are fabricated in the InGaAsP material system and their static and dynamic features are compared. The coupled-cavity lasers show a larger lasing efficiency and generate an output power higher than the single-cavity lasers, results that are consistent with the theoretical results obtained by rate equations. In dynamic regime, the single-cavity lasers produce pulses as short as 113 ps, while the coupled-cavity lasers show a significantly longer lasing duration. These results indicate that the photonic crystal laser is a promising candidate for the light source in high-speed photonic integrated circuit.

III–V-on-Si Photonic Crystal Nanocavity Laser Technology for Optical Static Random Access Memories

Heterogeneous integration of III-V semiconductors on silicon has gained considerable momentum fueled by the need to implement fully functional photonic devices and circuits in a CMOS compatible platform. In this communication, we report on a III-V photonic crystal (PhC) nanocavity, heterogeneously integrated on a silicon-on-insulator platform, to form a PhC nanocavity laser capable of exhibiting two elementary static random access memory (SRAM) cell functions individually, namely switching and latching operations under a high-speed, bit-level regime. As such, the PhC nanocavity laser is examined as a generic logic functions building block, suitable toward multiGb/s energy-efficient, optical SRAM cells with minimal device footprint. The proposed device occupies a total area of only 6.2 μm2 , rendering in this way the demonstrated memory element the smallest among the integrated optical memories presented so far. Bit-level SRAM cell operation requires two elementary functions: the access gate (AG) switching function and set-reset flip-flop (SR-FF) latching function. At first, AG switching operation is evaluated through successful wavelength conversion at 10 Gb/s, revealing a power penalty of 1 dB at 10–9 BER and a switching energy of only 4.8 fJ/bit. Then, fully functional SR-FF memory operation is successfully demonstrated, exhibiting error-free operation with negative power penalty at 5 Gb/s and switching energies of 6.4 fJ/bit. FF operation at higher speeds of 10 Gb/s with reduced switching energy levels of 3.2 fJ/bit is also experimentally investigated. Both logic operations were demonstrated separately with the same PhC nanocavity laser device exhibiting <50 ps switching times and evaluated under real-type data traffic patterns, raising expectations for beyond 20 Gb/s capabilities toward implementing energy-efficient, ultracompact and high-speed true optical SRAM setups for Datacom applications.

Modulation of carrier dynamics and threshold characteristics in 1.3-μm quantum dot photonic crystal nanocavity lasers

A self-consistent all-pathway quantum dot (QD) rate equation model, in which all possible relaxation pathways are considered, is used to investigate the influence of quality (Q) factor on the carrier dynamics of 1.3-μm InAs/GaAs QD photonic crystal (PhC) nanolasers. It is found that Q factor not only affects the photon lifetime, but also modulates the carrier occupation in QDs. About three times increases of carrier injection efficiency in QD ground state can be realized in nanocavity with high Q factor. However, it also reveals that over 90% improvement of threshold current happens when Q factor increases from 2000 to 7000, which means it might be not necessary to pursuit for ultrahigh Q factor for the purpose of low threshold current.

Systematic study of thresholdless oscillation in high-β buried multiple-quantum-well photonic crystal nanocavity lasers

Buried multiple-quantum-well (MQW) 2D photonic crystal cavities (PhC) achieve low non-radiative recombination and high carrier confinement thus making them highly efficient emitters. In this study, we have investigated the lasing characteristics of high-β(spontaneous emission coupling factor) buried MQW photonic crystal nanocavity lasers to clarify the theoretically-predicted thresholdless operation in high-β nanolasers. The strong light and carrier confinement and low non-radiative recombination in our nanolasers have enabled us to clearly demonstrate very smooth lasing transition in terms of the light-in vs light-out curve and cavity linewidth. To clarify the thresholdless lasing behavior, we carried out a lifetime measurement and a photon correlation measurement, which also confirmed the predicted behavior. In addition, we systematically investigated the dependence of β on the detuning frequency, which was in good agreement with a numerical simulation based on the finite-difference time-domain method. This is the first convincing systematic study of nanolasers based on an MQW close to the thresholdless regime.

Frequency-doubled photonic crystal nanocavity lasers

Frequency-doubled photonic crystal nanocavity lasers

Self-frequency summing in quantum dot photonic crystal nanocavity lasers

We demonstrate self-frequency summing in photonic crystal nanocavity lasers with quantum dot gain. Two dipole modes and a hexapole mode, supported in the cavity, simultaneously showed lasing oscillation in the near infrared wavelength region under optical carrier injection. Meanwhile, within the same laser cavity, the internally generated three laser fields are up-converted to exhibit sharp visible emission lines via intra-cavity nonlinear frequency summing (and doubling) processes. This self-frequency summing process in active nanocavities will pave the way for developing nanoscale nonlinear optical light sources.

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

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.

Silicon-based three-dimensional photonic crystal nanocavity laser with InAs quantum-dot gain

We report on the demonstration of lasing oscillation in a silicon-based three-dimensional photonic crystal nanocavity using InAs quantum dots as gain material by pulsed optical pumping at 11 K. An active layer embedding InAs quantum dots was inserted in the cavity using micromanipulation technique. The highest quality factor for silicon-based three-dimensional photonic crystal cavities (∼22 000) was achieved. We also evaluated the spontaneous emission coupling factor of the laser to be ∼0.78 by fitting the experimental light-in light-out curve with coupled rate equations. This result would pave the way to the realization of CMOS-compatible high-density three-dimensional photonic integrated circuits.

Narrow linewidth operation of buried-heterostructure photonic crystal nanolaser

We investigate the spectral linewidth of a monolithic photonic crystal nanocavity laser. The nanocavity laser is based on a buried heterostructure cavity in which an ultra-small InGaAsP active region is embedded in an InP photonic crystal. Although it was difficult to achieve narrow linewidth operation in previously reported photonic crystal nanocavity lasers, we have successfully demonstrated a linewidth of 143.5 MHz, which is far narrower than the cold cavity linewidth and the narrowest value yet reported for nanolasers and photonic crystal lasers. The narrow linewidth is accompanied by a low power consumption and an ultrasmall footprint, thus making this particular laser especially suitable for use as an integrated multi-purpose sensor.

Photonic crystal nanocavity laser in an optically very thick slab

A photonic crystal (PhC) nanocavity formed in an optically very thick slab can support reasonably high-Q modes for lasing. Experimentally, we demonstrate room-temperature pulsed lasing operation from the PhC dipole mode emitting at 1324 nm, which is fabricated in an InGaAsP slab with thickness (T) of 606 nm. Numerical simulation reveals that when T≥800 nm, over 90% of the laser output power couples to the PhC slab modes, suggesting a new route toward an efficient in-plane laser for photonic integrated circuits.

Phase-locking regimes of photonic crystal nanocavity laser arrays

We model and analyze the dynamical properties of coupled photonic crystal nanocavity lasers. The model includes Purcell enhancement of the spontaneous emission and intercavity coupling. The coupling strength between neighboring cavities is an essential parameter, and by performing finite-difference time-domain calculations, the typical coupling strength is extracted for realistic structures. Phase-locking regimes are identified, and their stability with respect to parameter variation is investigated. The results suggest that quantum well devices are not well suited for phase-locked nanocavity laser array devices.

One-dimensional photonic crystal nanobeam lasers on a flexible substrate

We demonstrate a one-dimensional (1D) photonic crystal (PhC) nanocavity laser composed of hybrid PhC mirrors on a suspended nanobeam (NB) with very small device footprint of 8.5 × 0.57 μm2. The 0th-order mode lasing action with low threshold of 280 μW is observed. Via the optical glue stamping process, the devices are directly transferred onto a flexible polypropylene substrate. Single mode lasing action with effective threshold of 17 μW is achieved. The robust lasing properties of the device with different bending radii R from ∞ to 2.5 mm are obtained. Via finite-element method, we also theoretically address that the lasing wavelength is almost invariant when R &amp;gt; 1.0 mm. This flexible 1D PhC NB laser will be a good candidate for efficient nanolaser in future flexible photonic integrated circuits with ultrahigh component density.

Ultralow-threshold electrically pumped quantum-dot photonic-crystal nanocavity laser

Efficient, low threshold, and compact semiconductor laser sources are being investigated for many applications in high-speed communications, information processing, and optical interconnects. The best edge-emitting and vertical cavity surface-emitting lasers (VCSELs) have thresholds on the order of 100 \muA[1,2] but dissipate too much power to be practical for many applications, particularly optical interconnects[3]. Optically pumped photonic crystal (PC) nanocavity lasers represent the state of the art in low-threshold lasers[4,5]; however, in order to be practical, techniques to electrically pump these structures must be developed. Here we demonstrate a quantum dot photonic crystal nanocavity laser in gallium arsenide pumped by a lateral p-i-n junction formed by ion implantation. Continuous wave lasing is observed at temperatures up to 150 K. Thresholds of only 181 nA at 50 K and 287 nA at 150 K are observed - the lowest thresholds ever observed in any type of electrically pumped laser.

A reversibly tunable photonic crystal nanocavity laser using photochromic thin film

We demonstrate a reversibly tunable photonic crystal quantum dot laser using a photochromic thin film. The laser is composed of a photonic crystal cavity with a bare cavity Q as high as 4500 coupled to a high density ensemble of indium arsenide quantum dots. By depositing a thin layer of photochromic material on the photonic crystal cavities, the laser can be optically tuned smoothly and reversibly over a wavelength range of 2.68 nm. Lasing is observed at temperatures as high as 80 K in the 900-1000 nm near-infrared wavelength range. The spontaneous emission coupling factor is measured to be as high as β=0.41, indicating that the laser operates in the high-β regime.

20-Gbit/s directly modulated photonic crystal nanocavity laser with ultra-low power consumption

We have demonstrated an ultracompact buried heterostructure photonic crystal (PhC) laser, consisting of an InGaAsP-based active region (5.0 x 0.3 x 0.15 μm3) buried in an InP layer. By employing a buried heterostructure with an InP layer, we can greatly improve thermal resistance and carrier confinement. We therefore achieved a low threshold input power of 6.8 μW and a maximum output power in the output waveguide of -10.3 dBm by optical pumping. The output light is effectively coupled to the output waveguide with a high external differential quantum efficiency of 53%. We observed a clear eye opening for a 20-Gbit/s NRZ signal modulation with an absorbed input power of 175.2 μW, resulting in an energy cost of 8.76 fJ/bit. This is the smallest reported energy cost for any type of semiconductor laser.

Zero-cell photonic crystal nanocavity laser with quantum dot gain

We demonstrate laser oscillation in a hexagonal-lattice photonic crystal nanocavity using an InGaAs quantum dot gain material by optical pumping at 5 K. The cavity comprises a defect created by shifting several air holes in a two-dimensional photonic crystal slab structure without removing any air holes to achieve both small mode volume and a high cavity quality factor. The measured cavity quality factors and estimated mode volume for the nanocavity are ∼33 000 and 0.004 μm3 [0.23(λ0/n)3]. The laser threshold is compared between the zero-cell and L3-type nanocavity lasers, and the zero-cell nanolasers are found to have lower thresholds of about one-third of the L3-type nanolasers. This result suggests that a higher Purcell factor of the zero-cell nanolaser is reflected as a lower laser threshold.

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

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.

Design, fabrication and optical characterization of GaAs photonic crystal nanocavity lasers with InAs quantum dots gain wafer-bonded onto Si substrates

We designed and fabricated III–V compound semiconductor two-dimensional photonic crystal (PhC) thin film slabs with quantum dots (QDs) inside formed on Si substrates for highly integrated silicon photonic circuits with built-in nanolasers. Defect-shifted L3 type PhC nanocavities formed in GaAs thin films embedding 1.3 μm-emitting InAs QDs layer-transferred onto Si substrates were investigated. Quality factors <1000 for the PhC nanocavities on SiO 2 were enhanced up to ∼8000 by removing SiO 2 to form air-bridge structures, resulting in room temperature, continuous wave lasing.