Microring Lasers Research Articles

High-efficiency single-mode erbium-doped lithium niobate microring laser with milliwatt output power

High-efficiency single-mode erbium-doped lithium niobate microring laser with milliwatt output power

Coexistence of the Radial-Guided Mode and WGM in Azimuthal-Grating-Integrated Microring Lasers

Coexistence of the Radial-Guided Mode and WGM in Azimuthal-Grating-Integrated Microring Lasers

(Invited) Shape Engineering of Nanostructured III-V Semiconductor Lasers

Group III-V semiconductors have revolutionised electronics and optoelectronics due to their superior physical and optoelectronic properties including high carrier mobility, direct bandgap and band structure engineering capability. Reducing the device size to nanoscale brings many unique properties, such as large surface-area-to-volume ratio, high aspect ratio, carriers and photons confinement effect. These nanostructures have already been demonstrated for potential applications in light emitters, photodetectors, solar cells and for photoelectrochemical water splitting. However, to date most efforts on the growth of these nanostructures have been limited to nanowires.In this talk, we demonstrate selective area growth of III-V nanostructures, showing the possibility of obtaining other functional nanostructures, beyond the limitation of rod-like geometry. We demonstrate that by changing the pattern design on the mask and growth conditions, we are able to grow and control the shapes to form nanostructures such as membranes, flowers, rings, spirals, stars, ellipses etc. These shape-engineered nanostructures open up possibilities of new applications based on devices with novel geometries.In particular, we will show the results of our InP micro-ring lasers which have excellent cavity due to the atomically flat facets. Micro-disk and micro-ring lasers are light emitting devices that operate in the whispering gallery mode. They are important components for integrated photonics applications as light from can these devices can be efficiently coupled to on-chip waveguides. By coupling the micro-ring laser to a nanowire antenna, we further demonstrate that we can tune the emission directionality to the device.

Electrically pumped GeSn micro-ring lasers

Electrically pumped GeSn micro-ring lasers

(Dielectric Science &Technology Thomas D. Callinan Award) Semiconductor Nanostructures for Optoelectronics and Energy Applications

Semiconductors have played an important role in the development of information and communications technology, solar cells, solid state lighting. Nanowires are considered as building blocks for the next generation electronics and optoelectronics. In this talk, I will present the results on growth of nanowires, nanomembranes and microrings and their optical properties. Then I will discuss theoretical design and experimental results on optoelectronic devices. In particular I will discuss nanowire and micro-ring lasers and integration of nanowires and microrings. I will also present the results on polarization sensitive, broad bandwidth THz detectors operating at room temperature. Nanowire based energy devices such as solar cells and photoelectrochemical (PEC) water splitting will be discussed. I will discuss about Neuro-electrodes to study brain signaling to understand dementia. Future prospects of the semiconductor nanostructures will be discussed.

Single-mode lasing by tailoring the excitation of localized surface plasmon resonances to whispering gallery modes in a microring laser.

Cavity mode manipulation in lasers is urgent for the stable single-mode operation of a microring laser. Here, we propose and experimentally demonstrate the plasmonic whispering gallery mode microring laser for strong coupling between local plasmonic resonances and whispering gallery modes (WGM) on the microring cavity to achieve pure single-mode lasing. The proposed structure is fabricated based on integrated photonics circuits consisting of gold nanoparticles deposited on a single microring. Additionally, our numerical simulation provides deep insight into the interaction between the gold nanoparticles and WGM modes. The manufacture of microlasers for the advancement of lab-on-a-chip devices and all-optical detection of ultra-low analysts may benefit from our findings.

Monolithic Yb3+-doped thin film lithium niobate microring laser fabricated by photolithography-assisted chemo-mechanical etching technology

We demonstrate an on-chip microring laser on Y b 3 + -doped thin film lithium niobate (Yb:TFLN) fabricated by photolithography-assisted chemo-mechanical etching technology. Multiwavelength laser emissions around 1025 nm from the microring resonator pumped by a 980 nm laser diode are observed with the lasing threshold of 10 mW. Experimentally, up to 14 longitudinal modes are obtained from the fabricated Yb:TFLN microring laser, and this on-chip microring laser is a promising light source for multiple wavelength channels in optical communications and biosensors.

Unidirectional emission of GaN-on-Si microring laser and its on-chip integration

Abstract GaN-based microring lasers grown on Si are promising candidates for compact and efficient light sources in Si-based optoelectronic integration and optical interconnect due to their small footprints, low mode volume, low power consumption, and high modulation rate. However, the high symmetry of circular microcavity leads to isotropic emission, which not only reduces the light collection efficiency, but also affects other adjacent devices during data transmission. In this study, the unidirectional lasing emission of room-temperature current-injected GaN-based microring laser was realized by coating metal Ag on the microring sidewall and integrating a direct coupled waveguide. The light was efficaciously confined in the cavity and only emitted from the waveguide, which avoided optical signal crosstalk with other adjacent devices. Furthermore, we integrated a microdisk at the other end of the waveguide as a photodetector, which could effectively detect the output power of the microring laser from the direct coupled waveguide. Therefore, a preliminary on-chip integration of GaN-based microring laser, waveguide and photodetector on Si substrate was successfully demonstrated for the first time, opening up a new way for on-chip integration and optical interconnect on a GaN-on-Si platform.

Laser diode-pumped compact hybrid lithium niobate microring laser.

We demonstrate a compact hybrid lithium niobate microring laser by butt coupling a commercial 980-nm pump laser diode chip with a high-quality Er3+-doped lithium niobate microring chip. Single-mode lasing emission at 1531-nm wavelength from the Er3+-doped lithium niobate microring can be observed with the integrated 980-nm laser pumping. The compact hybrid lithium niobate microring laser occupies the chip size of 3 mm × 4 mm × 0.5 mm. The threshold pumping laser power is 6 mW and the threshold current is 0.5 A (operating voltage 1.64 V) at atmospheric temperature. The spectrum featuring single-mode lasing with small linewidth of 0.05 nm is observed. This work explores a robust hybrid lithium niobate microring laser source which has potential applications in coherent optical communication and precision metrology.

Defect-assisted, spray-printed colloidal quantum dot microlasers for biosensing.

This study successfully implements spectrally distinguishable CdSe-ZnS core-shell colloidal quantum dot (CQD) microlasers by a simple, efficient spray printing technique and demonstrates its potential in biosensing. We have systematically characterized the optical properties of printed microring lasers with diameters less than 60 µm. The smallest structure that can be excited has a diameter as small as 30 µm, which is much smaller than the counterparts prepared by piezoelectric ink-jet printing. The detection sensitivity of 4.54 nm/min/refractive index unit is verified in glucose sensing using a printed CQD microlaser. Biosensing of diverse glucose and bovine serum albumin solutions using printed microlasers with the assistance of defects demonstrates a new, to the best of our knowledge, prototype for the development of high-performance, low-cost on-chip microcavity sensors.

Routes to chaos in a class-B laser coupled to a neutral resonator

We study the dynamics of a class-B semiconductor microring laser coupled to a neutral microring resonator for common fabrication parameters. For zero detuning between the resonators, we identify five dynamical regions controlled by the normalized pump rate of the laser and coupling strength between the resonators. These regions show stable lasing with phase locking for either sufficiently small or large coupling strength parameter values. Multistability and chaos arise in between these stable regions where at least one fixed point is attractive. The transition from stable to unstable lasing regions in the parameter space phase diagram is a crossover.

Telecom InGaAs/InP Quantum Well Lasers Laterally Grown on Silicon-on-Insulator

To achieve on-chip lasers for Si-photonics, monolithic integration using selective epitaxy is a favorable option due to the unique defect engineering and resultant bufferless structure. Among the intensively investigated selective epitaxy methods, lateral aspect ratio trapping generates III-V devices in the same plane as the Si layer enabling efficient coupling with Si waveguides. Here, we demonstrate telecom InGaAs/InP quantum well lasers selectively grown on commercial silicon-on-insulator substrates with an in-plane structure using a simple structural design and growth scheme without any regrowth steps. Leveraging on the lateral aspect ratio trapping technique, uniform quantum wells with high crystalline quality were obtained and shown by comprehensive material characterizations. Room temperature pulsed lasing was achieved on the fabricated micro-ring lasers with a low threshold of 20 μJ/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The results present a crucial step towards electrically pumped lasers at telecom band as well as fully integrated Si-photonics.

Backscattering Effects on High-Speed Modulation of Strongly Injection-Locked Whistle-Geometry Semiconductor Ring Lasers

An injection-locking scheme, involving a single-frequency master laser monolithically integrated with a unidirectional whistle-geometry semiconductor microring laser, has been proposed for enhanced ultra-high-speed performance. Greatly enhanced high-speed modulation performance of the strong-injection-locking scheme has been predicted in numerical calculations. In our previous analysis, however, linear coupling between the two counter-propagating modes due to light backscattering was not taken into account. In this work, we investigate the potential negative impact of light backscattering between the two counter-propagating modes on high-speed modulation performance of strongly injection-locked unidirectional whistle-geometry semiconductor microring lasers.

3D-Printed Möbius Microring Lasers: Topology Engineering in Photonic Microstructures.

Manipulating photons in artificially structured materials is highly desired in modern photonic technology. Nontrivial topological structures are rapidly emerging as a state-of-art platform for achieving unprecedented fascinating phenomena of photon manipulation. However, the current studies mainly focus on planar structures, and the fabrication of photonic microstructures with specific topological geometric features still remains a great challenge. Extending the topological photonics to 3Dmicroarchitectures is expected to enrich the photon manipulation capabilities and further advance the topological photonic devices. Here, a femtosecond laser direct writing technique is employed to fabricate 3D topological Möbius microring resonators from dye-doped polymer. The high-quality-factor Möbius microring resonator supports a unique spin-orbit coupled lasing at very low threshold. Due to the spin-orbit coupling induced geometric/Berry phase, the Möbius microrings, in striking contrast with ordinary microrings, output laser signals with all polarization states. The manipulation of miniaturized coherent light sources in the fabricated Möbius microrings represents a significant step forward toward 3D topological photonics that offers a novel design philosophy for functional photonic and optoelectronic devices.

Research progress in lithium niobate on insulator lasers

<p indent="0mm">Lithium niobate on insulator (LNOI) is considered one of the most competitive integrated photonics platforms due to the excellent optical properties of lithium niobate crystal and their compatibility with semiconductor micro/nano processing. Based on the continuous improvement of micro-nano fabrication technology, various transmission and control devices, such as low-loss waveguides and high-quality factor micro-cavities, showing better performance than traditional bulk materials devices, have been realized on LNOI. However, as an essential part of integrated photonics, the research of LNOI laser has made a breakthrough recently. Lithium niobate is an indirect bandgap material and thus tough for electroluminescence. It is a feasible and straightforward scheme to realize optically pumped laser based on rare-earth ion doping. This paper summarizes our research group’s recent research progress on realizing microdisk, microring, and single-mode lasers based on rare-earth-ion-doped LNOI and related works from other groups. We hope this review could benefit the related research on the active devices on LNOI.

Monolithic single-frequency microring laser on an erbium-doped thin film lithium niobate fabricated by a photolithography assisted chemo-mechanical etching

We overcome the difficulty in realizing a monolithic waveguide-coupled microring laser integrated on an erbium-doped thin film lithium niobate (Er: TFLN) using a photolithography assisted chemo-mechanical etching (PLACE) technique. We demonstrate an integrated single-frequency microring laser operating around 1531 nm wavelength. The PLACE technique, enabling integrated Er: TFLN photonics with low propagation loss, can thus be used to realize low cost mass production of monolithic on-chip microlasers with applications ranging from optical communication and photonic integrated circuit (PIC) to precision metrology and large-scale sensing.

Non-reciprocal parity-time symmetry breaking based on magneto-optical and gain/loss double ring resonators

In this paper, we explore the operation of a nonreciprocal non-Hermitian system consisting of a lossy magneto-optical ring resonator coupled to another ring resonator with gain and loss, and we demonstrate that such a system can exhibit non-reciprocity-based broken parity-time (PT) symmetry and supports one-way exceptional points. The nonreciprocal PT-phase transition is analyzed with the use of both analytical tools based on coupled-mode theory and two-dimensional finite element method simulations. Our calculations show that the response of the system strongly depends on the regime of operation – broken or preserved PT-symmetry. This response is leveraged to show that the system can operate as an optical isolator or a one-way laser with functionality tuned by adjusting loss/gain in the second ring resonator. The proposed system can thus be promising for device applications such as magnetically or even optically switchable non-reciprocal devices and one-way micro-ring lasers.

Integrated ytterbium-doped lithium niobate microring lasers.

Integrated and stable microlasers are indispensable building blocks of micro-photonics. Here, we report the realization of an ytterbium-doped lithium niobate microring laser operating in the 1060-nm band under the pump of a 980-nm-band laser. The monolithic laser has a low threshold of 59.32 µW and relatively high output power of 6.44 µW, a state-of-the-art value for rare-earth ions-doped lithium niobate thin-film lasers. The monolithic laser with desirable performance and attractive scalability may find many applications in lithium niobite photonics.

Direct modulation of electrically pumped coupled microring lasers.

We demonstrate how the presence of gain-loss contrast between two coupled identical resonators can be used as a new degree of freedom to enhance the modulation frequency response of laser diodes. An electrically pumped microring laser system with a bending radius of 50 μm is fabricated on an InAlGaAs/InP MQW p-i-n structure. The room temperature continuous wave (CW) laser threshold current of the device is 27 mA. By adjusting the ratio between the injection current levels in the two coupled microrings, our experimental results clearly show a bandwidth improvement by up to 1.63 times the fundamental resonant frequency of the individual device. This matches well with our rate equation simulation model.

Single-Pulse Measurement of Orbital Angular Momentum Generated by Microring Lasers.

Optical beams with helical phase fronts carry orbital angular momentum (OAM). To exploit this property in integrated photonics, micrometer-scale devices that generate beams with well-defined OAM are needed. Consequently, lasers based on microring resonators decorated with azimuthal grating elements have been investigated. However, future development of such devices requires better methods to determine their OAM, as current approaches are challenging to implement and interpret. If a simple and more sensitive technique were available, OAM microring lasers could be better understood and further improved. In particular, despite most devices being pulsed, their OAM output has been assumed to be constant. OAM fluctuations, which are detrimental for applications, need to be quantified. Here, we fabricate quantum-dot microring lasers and demonstrate a simple measurement method that can straightforwardly determine the magnitude and sign of the OAM down to the level of individual laser pulses. We exploit a Fourier microscope with a cylindrical lens and then investigate three types of microring lasers: with circular symmetry, with "blazed" grating elements, and with unidirectional rotational modes. Our results confirm that previous measurement techniques obscured key details about the OAM generation. For example, while time-averaged OAM from our unidirectional laser is very similar to our blazed grating device, single-pulse measurements show that detrimental effects of mode competition are almost entirely suppressed in the former. Nevertheless, even in this case, the OAM output exhibits shot-to-shot fluctuations. Thus, our approach reveals important details in the underlying device operation that can aid in the improvement of micrometer-scale sources with pure OAM output.