Miniaturizing spectrometers to nanoscale

Optical spectrometers have been playing significant roles in our life since Sir Isaac Newton demonstrated in 1666.Up to now,they still majorly rely on the dispersion of light by prisms or gratings in free space.For in-situ measurements,it was a wide dream to miniaturize these spectrometers while keeping their resolution and spectral range.

Broadband Sheet Parametric Oscillator for x^((2)) Optical Frequency Comb Generation via Cavity Phase Matching

We demonstrate a broadband optical parametric oscillation,using a sheet cavity,via cavity phase-matching.A21.2 THz broad comb-like spectrum is achieved,with a uniform line spacing of 133.0 GHz,despite a relatively large dispersion of 275.4 fs^(2)/mm around 1064 nm.With 22.6% high slope efficiency,and 14.9 kW peak power handling,this sheet optical parametric oscillator can be further developed for x^((2)) comb.

Harnessing sub-comb dynamics in a graphene-sensitized microresonator for gas detection

Since their inception, frequency combs generated in microresonators, known as microcombs, have sparked significant scientific interests. Among the various applications leveraging microcombs, soliton microcombs are often preferred due to their inherent mode-locking capability. However, this choice introduces additional system complexity because an initialization process is required. Meanwhile, despite the theoretical understanding of the dynamics of other comb states, their practical potential, particularly in applications like sensing where simplicity is valued, remains largely untapped. Here, we demonstrate controllable generation of sub-combs that bypasses the need for accessing bistable regime. And in a graphene-sensitized microresonator, the sub-comb heterodynes produce stable, accurate microwave signals for high-precision gas detection. By exploring the formation dynamics of sub-combs, we achieved 2 MHz harmonic comb-to-comb beat notes with a signal-to-noise ratio (SNR) greater than 50 dB and phase noise as low as – 82 dBc/Hz at 1 MHz offset. The graphene sensitization on the intracavity probes results in exceptional frequency responsiveness to the adsorption of gas molecules on the graphene of microcavity surface, enabling detect limits down to the parts per billion (ppb) level. This synergy between graphene and sub-comb formation dynamics in a microcavity structure showcases the feasibility of utilizing microcombs in an incoherent state prior to soliton locking. It may mark a significant step toward the development of easy-to-operate, systemically simple, compact, and high-performance photonic sensors.

Near-zero-dispersion soliton and broadband modulational instability Kerr microcombs in anomalous dispersion

The developing advances of microresonator-based Ker cavity solitons have enabled versatile applications ranging from communication,signal processing to high-precision measurements.Resonator dispersion is the key factor determining the Kerr comb dynamics.Near the zero group-velocity-dispersion(GVD)regime,low-noise and broadband microcomb sources are achievable,which is crucial to the application of the Kerr soliton.When the GVD is almost vanished,higher-order dispersion can significantly affect the Kerr comb dynamics.Although many studies have investigated the Kerr comb dynamics near the zero-dispersion regime in microresonator or fiber ring system,limited by dispersion profles and dispersion perturbations,the near-zero-dispersion soliton structure pumped in the anomalous dispersion side is still elusive so far.Here,we theoretically and experimentally investigate the microcomb dynamics in fiber-based Fabry-Perot microresonator with ultra-small anomalous GVD.We obtain 2/3-octave-spaning microcombs with~10 GHz spacing,>84 THz span,and>8400 comb lines in the modulational instability(MI)state,without any external nonlinear spectral broadening.Such widely-spanned Ml combs are also able to enter the soliton state.Moreover,we report the first observation of anomalous-dispersion based near-zero-dispersion solitons,which exhibits a local repetition rate up to 8.6 THz,an individual pulse duration<100 fs,a span>32 THz and>3200 comb lines.These two distinct comb states have their own advantages.The broadband MI combs possess high conversion efficiency and wide existing range,while the near-zero-dispersion soliton exhibits relatively low phase noise and ultra-high local repetition rate.This work complements the dynamics of Kerr cavity soliton near the zero-dispersion regime,and may stimulate cross-disciplinary inspirations ranging from dispersion-controlled microresonators to broadband coherent comb devices.

Noise canceled graphene-microcavity fiber laser sensor for ultrasensitive gas detection

Optical microcavities offer a promising platform for highly efficient light–matter interactions.Recently,the combination of microresonators and 2D materials in the nanoscale has further enriched the optoelectronics of microcavity geometries,spurring broad advances including lasers,nonlinear converters,modulators,and sensors.Here,we report the concept of compact dual-laser cogeneration in a graphene-microcavity fiber,which offers a way to cancel the optical common mode noises.Driven by a single 980 nm pump,orthogonally polarized laser lines are generated in a pair of degeneracy breaking modes.The two laser lines produce a heterodyne beat note at 118.96 MHz,with frequency noise down to 200 Hz~2∕Hz at 1 MHz offset,demonstrating a linewidth of 930 Hz in vacuum.This compact device enables on-line and label-free NH_(3) gas detection with high resolution,realizing a detection limit on a single pmol/L level,and a capability to quantitatively trace gas–graphene interactions.Such a combination of graphene optoelectronics and microcavity photonics demonstrates a novel physical paradigm for microlaser control and offers a new scheme for in situ chemical sensing.

Biochemical sensing in graphene-enhanced microfiber resonators with individual molecule sensitivity and selectivity

Photonic sensors that are able to detect and track biochemical molecules offer powerful tools for information acquisition in applications ranging from environmental analysis to medical diagnosis.The ultimate aim of biochemical sensing is to achieve both quantitative sensitivity and selectivity.As atomically thick films with remarkable optoelectronic tunability,graphene and its derived materials have shown unique potential as a chemically tunable platform for sensing,thus enabling significant performance enhancement,versatile functionalization and flexible device integration.Here,we demonstrate a partially reduced graphene oxide(prGO)inner-coated and fiber-calibrated Fabry-Perot dye resonator for biochemical detection.Versatile functionalization in the prGO film enables the intracavity fluorescent resonance energy transfer(FRET)to be chemically selective in the visible band.Moreover,by measuring the intermode interference via noise canceled beat notes and locked-in heterodyne detection with Hz-level precision,we achieved individual molecule sensitivity for dopamine,nicotine and single-strand DNA detection.This work combines atomic-layer nanoscience and high-resolution optoelectronics,providing a way toward high-performance biochemical sensors and systems.

Electrically controllable laser frequency combs in graphene-fibre microresonators

Laser frequency combs emitting ultrafast pulses of light,at equidistantly discrete frequencies,are cornerstones of modern information networks.In recent years,the generation of soliton combs in microcavities with ultrahighquality factors has established microcombs as out-oflaboratory tools.However,the material and geometry of a laser cavity,which determine comb formation,are difficult to electrically tune.Such dynamic control can further enrich the diversity of comb outputs and help to actively stabilize them.

Emerging material platforms for integrated microcavity photonics

Many breakthroughs in technologies are closely associated with the deep understanding and development of new material platforms.As the main material used in microelectronics,Si also plays a leading role in the development of integrated photonics.The indirect bandgap,absence ofχ(2)nonlinearity and the parasitic nonlinear absorptions at the telecom band of Si imposed technological bottlenecks for further improving the performances and expanding the functionalities of Si microcavities in which the circulating light intensity is dramatically amplified.The past two decades have witnessed the burgeoning of the novel material platforms that are compatible with the complementary metal-oxide-semiconductor(COMS)process.In particular,the unprecedented optical properties of the emerging materials in the thin film form have resulted in revolutionary progress in microcavity photonics.In this review article,we summarize the recently developed material platforms for integrated photonics with the focus on chip-scale microcavity devices.The material characteristics,fabrication processes and device applications have been thoroughly discussed for the most widely used new material platforms.We also discuss open challenges and opportunities in microcavity photonics,such as heterogeneous integrated devices,and provide an outlook for the future development of integrated microcavities.

Optical rogue wave in random fiber laser

The famous demonstration of optical rogue waves(RWs),a powerful tool to reveal the fundamental physics in different laser scenarios,opened a flourishing time for temporal statistics.Random fiber laser(RFL)has likewise attracted wide attention due to its great potential in multidisciplinary demonstrations and promising applications.However,owing to the distinctive cavity-free structure,it is a scientific challenge to achieve temporal localized RWs in RFLs,whose feedback arises from multiple scattering in disordered medium.Here,we report the exploration of RW in the highly skewed,transient intensity of an incoherently pumped RFL for the first time,to our knowledge,and unfold the involved kinetics successfully.The corresponding frequency domain measurements demonstrate that the RW event arises from a crucial sustained stimulated Brillouin scattering process with intrinsic stochastic nature.This investigation highlights a novel path to fully understanding the complex physics,such as photon propagation and localization,in disordered media.

Kilometers Long Graphene-Coated Optical Fibers for Fast Thermal Sensing

The combination of optical fiber with graphene has greatly expanded the application regimes of fiber optics,from dynamic optical control and ultrafast pulse generation to high precision sensing.However,limited by fabrication,previous graphene-fiber samples are typically limited in the micrometer to centimeter scale,which cannot take the inherent advantage of optical fibers—longdistance optical transmission.Here,we demonstrate kilometers long graphene-coated optical fiber(GCF)based on industrial graphene nanosheets and coating technique.The GCF shows unusually high thermal diffusivity of 24.99 mm^(2) s^(-1) in the axial direction,measured by a thermal imager directly.This enables rapid thermooptical response both in optical fiber Bragg grating sensors at one point(18-fold faster than conventional fiber)and in long-distance distributed fiber sensing systems based on backward Rayleigh scattering in optical fiber(15-fold faster than conventional fiber).This work realizes the industrial-level graphene-fiber production and provides a novel platform for two-dimensional material-based optical fiber sensing applications.

Graphene-Fiber Biochemical Sensors: Principles, Implementations, and Advances

Single atomically thick graphene, with unique structural flexibility, surface sensitivity, and effective light-mater interaction, has shown exceptional advances in optoelectronics. It opens a door for diverse functionalized photonic devices, ranging from passive polarizers to active lasers and parametric oscillators. Among them, graphene-fiber biochemical sensors combine the merits of both graphene and fiber structures, demonstrating impressively high performances, such as single-molecule detectability and fast responsibility. These graphene-fiber biochemical sensors can offer tools in various applications, such as gas tracing, chemical analysis, and medical testing. In this paper, we review the emerging graphene-fiber biochemical sensors comprehensively, including the sensing principles, device fabrications, systematic implementations, and advanced applications. Finally, we summarize the state-of-the-art graphene-fiber biochemical sensors and put forward our outlooks on the development in the future.