Tao Wang

Tao Wang
Hangzhou Dianzi University · School of Electronics and Information

Dr.

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74
Publications
8,178
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553
Citations

Publications

Publications (74)
Article
Since the development of micro- and nanolasers, the question of laser threshold has been subject to debate. Different definitions have been used to try and establish its occurrence, often encountering major obstacles. We examine a set of common physical definitions which we apply to measurements taken in a micro-VCSEL. Their predictions not only cl...
Article
Photonic crystal lasers with a high-Q factor and small mode volume are ideal light sources for on-chip nano-photonic integration. Due to the submicron size of their active region, it is usually difficult to achieve high output power and single-mode lasing at the same time. In this work, we demonstrate well-selected single-mode lasing in a line-defe...
Preprint
Full-text available
Since the development of micro- and nanolasers, the question of laser threshold has been subject to debate. Different definitions have been used to try and establish its occurrence, often encountering major obstacles. We examine a set of common physical definitions which we apply to measurements taken in a micro-VCSEL. Their predictions not only cl...
Article
Full-text available
Lasers distinguish themselves for the high coherence and high brightness of their radiation, features which have been exploited both in fundamental research and a broad range of technologies. However, emerging applications in the field of imaging, which can benefit from brightness, directionality and efficiency, are impaired by the speckle noise su...
Article
Full-text available
In this work, we propose and numerically investigate a two-dimensional microlaser based on the concept of bound states in the continuum (BIC). The device consists of a thin gain layer (Rhodamine 6G dye-doped silica) sandwiched between two high-contrast-grating layers. The structure supports various BIC modes upon a proper choice of topological para...
Article
Full-text available
Extreme confinement of electromagnetic waves and mechanical displacement fields to nanometer dimensions through plasmonic nanostructures offers unprecedented opportunities for greatly enhanced interaction strength, increased bandwidth, lower power consumption, chip-scale fabrication and efficient actuation of mechanical systems at the nanoscale. Co...
Preprint
Full-text available
Chaos in semiconductor lasers or other optical systems have been intensively studied in past two decades. However, the route from period doubling to chaos is still not sufficiently visible, in particular, in gain-modulated semiconductor lasers. In this article we perform a careful investigation of the route to chaos exhibited by directly modulated...
Article
We propose a new sensing method based on the measurement of the second-order autocorrelation of the output of micro- and nanolasers with intensity feedback. The sensing function is implemented through the feedback-induced threshold shift, whose photon statistics is controlled by the feedback level in a characteristic way for different laser sizes....
Preprint
Full-text available
Extreme confinement of electromagnetic waves and mechanical displacement fields to nanometer dimensions through plasmonic nanostructures offers unprecedented opportunities for greatly enhanced interaction strength, increased bandwidth, lower power consumption, chip-scale fabrication and efficient actuation of mechanical systems at the nanoscale. Co...
Preprint
Full-text available
We propose a new sensing method based on the measurement of the second-order autocorrelation of the output of micro- and nanolasers with intensity feedback. The sensing function is implemented through the feedback-induced threshold shift, whose photon statistics is controlled by the feedback level in a characteristic way for different laser sizes....
Preprint
Full-text available
In this work, we propose and numerically investigate a two-dimensional microlaser based on the concept of bound states in the continuum (BIC). The device consists of a thin gain layer (Rhodamine 6G dye-doped silica) sandwiched between two high-contrast-grating layers. The structure supports various BIC modes upon a proper choice of topological para...
Poster
Full-text available
Passive plasmonic sensors are reported with ample configurations, but optical loss hinders the further improvement of their sensing performance. This shortcoming can be overcome by gain-assistant plasmonic structure. In this work, an active biosensor is designed based on plasmonic crystal laser which exhibits ultra-high figure of merit (FOM) for bo...
Article
Nanolasers are considered ideal candidates for communications and data processing at the chip-level thanks to their extremely reduced footprint, low thermal load and potentially outstanding modulation bandwidth, which in some cases has been numerically estimated to exceed hundreds of GHz. The few experimental implementations reported to date, howev...
Article
Plasmonic lasers provide a paradigm-changing approach for the generation of coherent light at the nanoscale. In addition to the usual properties of coherent radiation, the emission of plasmonic lasers can feature high sensitivity to the surrounding environment, which makes this technology attractive for developing high-performance and highly-integr...
Article
Self-powered acceleration sensors based on triboelectric nanogenerators (TENGs) are critical components for vibration detection, which have promising applications in Internet of Things, wearable electronics and sensor networks. However, the development of this sensor is restricted by lack of the working mechanism. Herein, we propose a novel theoret...
Preprint
Nanolasers are considered ideal candidates for communications and data processing at chip-level thanks to their extremely reduced footprint, low thermal load and potentially outstanding modulation bandwidth, which in some case has been numerically estimated to exceed hundreds of GHz. The few experimental implementations reported to date, however, h...
Preprint
Plasmonic lasers provide a paradigm-changing approach for the generation of coherent light at the nanoscale. In addition to the usual properties of coherent radiation, the emission of plasmonic lasers can feature high sensitivity to the surrounding environment, which makes this technology attractive for developing high-performance and highly-integr...
Article
The miniaturization of optical sensors is a key step towards the development of highly integrated optical sensing techniques and devices. The present work proposes an ultra-compact organic vertical-cavity microlaser based on an active micro-pillar design, and explores its potential applications as a highly integrated gas sensor. The vertical-cavity...
Article
Full-text available
Photon statistical measurements on a semiconductor microlaser, obtained using single-photon counting techniques, show that a newly discovered pulsed emission regime is inconsistent with all current theoretical modeling. The observed spike dynamics, typical of small-scale devices, is at the origin of an unexpected discordance between the probability...
Article
Full-text available
Plasmonic nanocavities have proved to confine electromagnetic fields into deep subwavelength volumes, implying their potentials for enhanced optical trapping and sensing of nanoparticles. In this review, the fundamentals and performances of various plasmonic nanocavity geometries are explored with specific emphasis on trapping and detection of smal...
Article
Full-text available
Using a fully stochastic numerical scheme, we theoretically investigate the behavior of a nanolaser in the lasing transition region under the influence of intensity feedback. Studying the input-output curves as well as the second-order correlations for different feedback fractions, we obtain an insight into the role played by the fraction of photon...
Article
Spontaneous photon bursts are observed in the output collected from a mesoscale semiconductor-based laser near the lasing threshold. Their appearance is compared to predictions obtained from Laser Rate Equations and from a Stochastic Laser Simulator. While the latter is capable of predicting the observed large photon bursts, the photon numbers comp...
Article
The ability of laser systems to emit different adjustable temporal pulse profiles and patterns is desirable for a broad range of applications. While passive mode-locking techniques have been widely employed for the realization of ultrafast laser pulses with mainly Gaussian or hyperbolic secant temporal profiles, the generation of versatile pulse sh...
Article
Full-text available
Mechanical energy has been widely harvested to meet the increasing worldwide energy demands, especially propelled by the breakthrough of Triboelectric nanogenerator (TENG). Although extensive progresses have been achieved in the development of TENGs to harvest low-frequency mechanical energy, the collection of ultralow frequency mechanical energy l...
Preprint
Full-text available
Using a fully stochastic numerical scheme, we investigate the behaviour of a nanolaser in the low-coherence regime at the transition between spontaneous emission and lasing under the influence of intensity feedback. Studying the input-output curves as well as the second order correlations for different feedback fractions, we obtain an insight on th...
Preprint
Semiconductor lasers are notoriously sensitive to optical feedback, and their dynamics and coherence can be significantly modified through optical reinjection. We concentrate on the dynamical properties of a very small (i.e., microscale) Vertical Cavity Surface Emitting Laser (VCSEL) operated in the low coherence region between the emission of (par...
Preprint
Full-text available
Spontaneous photon bursts are observed in the output collected from a mesoscale semiconductor-based laser near the lasing threshold. Their appearence is compared to predictions obtained from Laser Rate Equations and from a Stochastic Laser Simulator. While the latter is capable of predicting the observed large photon bursts, the photon numbers comp...
Article
Full-text available
Semiconductor lasers are notoriously sensitive to optical feedback, and their dynamics and coherence can be significantly modified through optical reinjection. We concentrate on the dynamical properties of a very small (i.e., microscale) Vertical Cavity Surface Emitting Laser (VCSEL) operated in the low coherence region between the emission of (par...
Article
The generation of optical pulses at ultra-low bias level, thus low energy cost, is explored in a commercial micro-cavity semiconductor laser in view of testing the principle of energy efficient information encoding in potential integrated schemes. Sequences of regular, highly nonlinear pulses with acceptable amplitude stability are obtained from a...
Preprint
Full-text available
The generation of optical pulses at ultra low bias level, thus low energy cost, is explored in a commercial microcavity semiconductor laser in view of testing the principle of energy efficient information encoding in potential integrated schemes. Sequences of regular, highly nonlinear pulses with acceptable amplitude stability are obtained from a c...
Article
Lasing emission occurs only after crossing a threshold – the onset of coherence. In the smallest commercial microcavites (and even more so in nanolasers) identification of the threshold becomes problematic, but remains indispensable for the correct exploitation of the laser features. In article 1800086, Tao Wang and co‐workers propose a simple proc...
Article
A simple technique for identifying the onset of coherent emission in mesoscale lasers, which makes use of a small‐amplitude modulation added to the pump, is introduced. The optimal modulation frequency is obtained from the radio‐frequency power spectrum of the unperturbed laser emission. The identification of the lasing onset rests on the appearanc...
Conference Paper
Nanophotonic components operate in the few-photon regime, thus their experimental characterization calls for photon-counting techniques, at least in the threshold region, and requires adequate laser models to interpret the observations. While the photon statistics of (macroscopic) Class A [1] lasers is well understood and can be readily reconstruct...
Article
Full-text available
We present a simple and flexible technique for identifying the onset of coherent emission in lasers, from the mesoscale to the nanoscale, which makes use of photon counting and a small amplitude modulation added to the pump. The optimal modulation frequency is obtained from the radiofrequency power spectrum of the unperturbed laser emission. The id...
Conference Paper
Exploiting a single figure-eight laser configuration that uses a highly nonlinear on-chip spiral waveguide, we experimentally demonstrate several mode-locking dynamics. We adjust the mode-locking pulse profiles in a controlled manner by varying the polarization.
Conference Paper
Full-text available
Light with superthermal properties is experimentally observed in the emission of a room-temperature, electrically-pumped single mode microcavity for pump values below continuous lasing. The observations are compared to Generalized Laser Rate Equations and stochastic simulations.
Conference Paper
The concept of laser threshold loses its meaning in micro- and nanocavities due to finite-size effects amd unfolds into an ensemble of characteristic points. We demonstrate the measurement of indicators which identify the different points.
Article
The threshold properties of very small lasers (down to the nanoscale) are a topic of active research in light of continuous progress in nanofabrication. With the help of a simple rate equation model we analyze the intrinsic, macroscopic dynamics of threshold crossing for Class B lasers. We use the deterministic aspects of the basic rate equations t...
Conference Paper
We experimentally show how the nonlinear amplification properties of a micro-laser operating in the threshold region, sinusoidally modulated near its resonance (relaxation oscillations), can lead to several important advantages. First, suitably adjusting the bias point and the modulation amplitude, it is possible to obtain reliable trains of large...
Conference Paper
Nanolasers have steadily gained interest in the past years thanks to considerable technological advances. Interest in very small lasers dates back to the early 1980’s and considerable effort was placed throughout the 1990’s on understanding the threshold and coherence properties of the so-called thresholdless laser. Little progress has been made on...
Article
Full-text available
With the help of a simple rate equation model, we analyze the intrinsic dynamics of threshold crossing for Class B lasers. A thorough discussion of the characteristics and the limitations of this very commonly employed model, which provides excellent qualitative predictions on the laser behaviour, is offered. Approximate solutions for the populatio...
Conference Paper
Full-text available
The buildup of the coherence of a Class-B semiconductor microlaser in the sub-threshold region is characterized by photon coincidence. Correlation values g(2)(0) > 2 confirm the key role of spatio-temporal dynamics in the photon statistics.
Conference Paper
Nanolaser thresholds have been long debated. We propose a definition based on the dynamics of the laser output and a technique for its experimental detection in a mesoscale device. Modelling similarities forecast its useful extension to nanolasers.
Conference Paper
Full-text available
The nonlinear response of a Class-B semiconductor microlaser in the sub-threshold region is characterized through photon coincidence. Correlation values g(2)(0) > 3 confirm the key role of spatio-temporal dynamics in the photon statistics.
Poster
Full-text available
Lasers are often perceived as threshold devices, with a rapid, all-or-nothing transition around threshold. This approach usually holds fir high quality factor (class A) devices or macroscopic ones, but fails to correctly describe the transition in very small samples. The long carrier lifetime — compared to the cavity time — typical of semiconductor...
Article
Full-text available
We couple a double-channel imaging technique, allowing for the simultaneous acquisition of high-quality and high-resolution intensity and peak emission wavelength profiles [T. Wang and G. L. Lippi, Rev. Sci. Instrum. 86, 063111 (2015)], to the polarization-resolved analysis of the optical emission of a multimode vertical-cavity surface-emitting las...
Article
Full-text available
The classical description of laser field buildup, based on time-averaged photon statistics of Class A lasers, rests on a statistical mixture of coherent and incoherent photons. Here, applying multiple analysis techniques to temporal streams of data acquired in the threshold region of a Class B mesoscale laser, we conclusively show that new physics...
Article
We couple a double-channel imaging technique, allowing for the simultaneous acquisition of high-quality and high-resolution intensity and peak emission wavelength profiles [T. Wang and G.L. Lippi, Rev. Sci. Instr. 86, 063111 (2015)], to the polarization-resolved analysis of the optical emission of a multimode VCSEL. Detailed information on the loca...
Conference Paper
Full-text available
Nanolasers are currently at the focus of much research due to their potential as highly integrable, low-consumption and sub-microscopic footprint devices. Given the ultrahigh modulation speed which are projected for some of the most promising devices, modeling is being actively pursued to predict the modulation bandwidth achievable with these devic...
Conference Paper
Full-text available
The current technological advances on the nanoscale have allowed for remarkable progress in the fabrication of ever smaller lasers. High promise is expected from these unusual devices, whose potential application range from on-chip integration, fast and compact data handling, inclusion on non-invasive probes, etc. However, satisfactory modeling of...
Article
Full-text available
We report on a high-resolution double-channel imaging method used to synchronously map the intensity- and optical-frequency-distribution of a laser beam in the plane orthogonal to the propagation direction. The synchronous measurement allows us to show that the laser frequency is an inhomogeneous distribution below threshold, but that it becomes ho...
Conference Paper
Full-text available
The characterization of a laser beam is one of the core points around which are centered technological development and applications of lasers, since the progress is often based on a good knowledge of the properties of the laser beam. We propose a new technique which allows for obtaining high-resolution maps of the transverse beam profile of a laser...
Article
Zn1−xCuxO nanorods with different Cu concentrations are prepared by a hydrothermal method. Bent and aggregated nanorods are obtained, which is attributed to centripetal surface tension of the evaporation and coagulation processes of the water film on the ZnO nanorods. The broad visible band consists of one violet, three blue, and one green emission...
Article
The crystal structure and morphology of ZnO, grown on silicon substrate by two-step method, were measured by X-ray diffraction and field emission scanning electron microscopy. The results reveal that the sample is mainly composed of ZnO nanorods and preferentially oriented in the c-axis direction. The photoluminescence properties of the ZnO nanorod...
Article
A simple hydrothermal method is adopted to fabricate ZnO thin films on Si substrates. Surface topography of the samples evolves from thin nanosheets to hexagonal nanorods with increasing the growth time. The wetting behavior of all the samples can be reversibly switched from hydrophobicity to hydrophilicity, through alternation of UV illumination a...
Article
Full-text available
A simple hydrothermal method is adopted to fabricate ZnO thin films on Si substrates. Surface topography of the samples evolves from thin nanosheets to hexagonal nanorods with increasing the growth time. The wetting behavior of all the samples can be reversibly switched from hydrophobicity to hydrophilicity, through alternation of UV illumination a...
Article
Full-text available
In this work, one-dimensional (1D) and heavily doped Zn1−xCoxO (x = 0.05, 0.1, 0.15 and 0.2) nanorods (NRs) were successfully fabricated by a new solvothermal method. Such a Zn1−xCoxOnanorod exhibits a hexagonal prism-like microcrystal with a pyramidal top. Analyses from transmission electron microscopy (TEM) and high-resolution transmission electr...
Article
Depending on the ZnO seed-layers, a new kind of cobalt doped zinc oxide (Zn1−xCoxO) thin films with controllable morphology were prepared by a facile solvothermal method. A series of ZnO thin films with different Co contents were applied to study the effect of doped Co on morphology, structural and optical properties. It is found that the doped con...