Journal Club 2021 | Tanabe Photonic Structure Group

Journal Club

By fiscal year (April-December)

Fiscal Year 2021

Presentation Details:

The generation of perfect soliton crystals (PSCs) in subharmonic phase-modulated optical pumped microcavities is investigated numerically. A portion of the modulated pump frequency component is coupled into the microcavity through the vernier effect between the modulated pump mode and the resonator mode, forming a chirped periodic wave for soliton formation. Due to the increased pump efficiency, PSCs with 5-20 solitons have been demonstrated in micro optical resonators with FSRs around 10 GHz. Furthermore, it is shown that by removing the modulator, the pump power can be reduced while maintaining the PSC state. The scheme proposed in this study provides a new method for the study of soliton dynamics and increases the flexibility of soliton applications.

Presentation Details:

Free electron beams are versatile probes into microstructure and composition. The interaction of electrons and photons has led to significant developments in imaging methods and 4D microscopy techniques over the past decade. However, electron beams are typically only weakly coupled to light, and stronger interactions are required to control and detect electrons.
In this study, a whispering gallery mode resonator is used to couple the free electron beam with the resonator mode.
This successfully extends the spectral width of propagating electrons to 700 electron volts.

Presentation Details:

Optical integrated circuits have been attracting attention in recent years because they are inexpensive and enable the fabrication of chip-sized optical elements. Lasers are one of the most important elements in optical integrated circuits and have recently been fully integrated with SiN waveguides through multilayer heterogeneous integration. However, at telecommunication wavelengths, where photonics applications are concentrated, lasers with high device yield and high output power do not yet exist due to large mode transition losses, unoptimized resonator designs, and complex manufacturing processes. In this paper, we propose a new method to achieve this
We report a high-performance SiN laser with an output power of tens of milliwatts and a sub-kHz fundamental linewidth via a SiN waveguide, solving the problems described above.

Presentation Details:

Soliton combs have attracted attention as a compact optical frequency comb light source, but their conversion efficiency is low. In this paper, we demonstrate a highly efficient and broadband soliton comb by pulsed excitation of a silicon nitride resonator with low dispersion. The effect of excitation light jitter on the soliton comb is quantitatively clarified.

Presentation Details:

In this paper, we show that a frequency comb of microcavities excited by a single laser is used for high-speed data transmission using the IMDD scheme: 30 Gb/s NRZ modulation scheme and 60 Gb/s PAM4 modulation scheme with 120 Gb/s and 240 Gb/s data transmission, respectively, over 2 km of optical The data rates exceed the reachability, single-lane data rate, and aggregate data rate specified in the PSM4 (Parallel Single Mode) and CWDM4 (Course Wavelength Division Multiplex) multisource agreements. The extremely low power loss of 0.1dB compared to back-to-back characterization shows that high-speed data transmission using CMOS-compatible micro-resonator frequency comb is a feasible technology for the cost- and power-sensitive data center transceiver industry. The technology has been demonstrated to be feasible in the cost- and power-sensitive data center transceiver industry.

Presentation Details:

Metasurfaces are artificial materials composed of nanostructured subwavelength arrays, which enable versatile wavefront engineering as a tool for phase control. In this paper, we demonstrate a new mechanism of phase control by utilizing the topological features near the singularity of non-hermitian metasurfaces.

Presentation Details:

We have demonstrated a zero energy consumption method for resonance frequency tuning in silicon microring resonators by using a 3D printed microfluidic chip directly overlaid on an optical circuit. Different concentrations of NaCl solutions were used in the experiments, and resonant frequency shifts above the free spectral range were achieved at NaCl concentrations of, for example, 10%.

Presentation Details:

Controlling the topological properties of physical systems is fundamental to the development of defect-resistant devices and technologies. This paper proposes a photonic platform whose fundamental dynamics is driven and tuned by the interaction of topology, non-closeness, and nonlinearity. Using a photonic lattice of laser-written waveguides continuously ("gain") or split ("loss") coupled to interfacial defects, nonlinear control of parity-time symmetry and restoration or destruction of non-Hermitian topological states by nonlinearities are demonstrated. Such concepts can be applied to a wide range of non-Hermitian systems with intensity-dependent gains or losses, opening the possibility for new approaches to manipulate light.

Presentation Details:

Optical neural networks (ONNs) are implemented using cascaded Mach-Zehnder interferometers (MZIs) and are a potential alternative to traditional deep learning hardware. However, they require a large footprint due to MZI. This paper proposes a new solution to the problem by using a coupler with parity-time symmetry instead of MZI, and proposes the possibility of implementing ONNs with even higher speed and lower energy compared to the MZI implementation.

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Dissipative cur-solitons, mode-locked pulses generated in microcavities, are expected to have a variety of applications in communications and spectroscopy. However, it remains difficult to generate the fundamental soliton state deterministically. In this study, we show theoretically that it is possible to deterministically evolve not only the fundamental soliton state but also multiple soliton states and soliton crystal states by continuously applying a high-energy pulse trigger to an external continuous-wave driven pump. This method does not require scanning the continuous wave pump frequency and thus has the potential for turnkey soliton generation.

Presentation Details:

A 52-line superchannel was realized from a soliton microcom, achieving spectral efficiencies as high as 10 bit/s/Hz for 80 km transmission and 6 it/s/Hz for 2100 km transmission. The feasibility and advantages of generating broadband waveforms directly from the output of a microscale device at symbol rates close to the repetition rate of a comb were demonstrated.

Presentation Details:

In recent years, wavefront forming using scatterers has enabled optical operations that exceed conventional optical systems, such as aberration-free subwavelength focusing. However, input-output measurement of the scatterer is required, and the measurement challenge is a hurdle to practical use. Here, this paper is about overcoming this challenge by using random metasurfaces whose design is known in advance. Furthermore, by using the metasurface, imaging is performed with a high aperture focus extended to a field of view of about 8 mm.

Presentation Details:

We report on an optical MEMS using a SiO2 microtoroidal resonator. Using a WGM resonator with patterned electrodes, fast tuning of resonance modes by "capacitive tuning" is demonstrated. Such tuning enables efficient frequency conversion from radio frequency to optical frequency and application to optical switches.

Presentation Details:

Light sources of quantum light, especially correlated photon pairs that are indistinguishable in all degrees of freedom, are fundamental to optical quantum computation and simulation. Such light sources have recently been realized using integrated photonics, but their reliance on a single component, such as a ring resonator, limits their ability to tune the spectral and temporal correlation between the generated photons. In this study, a tunable source of indistinguishable photon pairs is realized using dual-pump spontaneous four-wave mixing in a topological system consisting of a two-dimensional array resonator. In this study, the spectral bandwidth was tuned by exploiting the linear dispersion of the topological edge states (by a factor of about 3.5), and the quantum interference between the generated photons was tuned by adjusting the two pump frequencies. We also demonstrated energy-time entanglement and confirmed the topological robustness of this light source using numerical simulations. The results of this study may lead to tunable frequency-multiplexed quantum light sources for realizing optical quantum technology.

Presentation Details:

Light with space-time orbital angular momentum (ST-OAM) is a recently discovered type of structured local electromagnetic field with a space-time spiral phase structure and transverse intrinsic orbital angular momentum. In this paper, the generation and characterization of the second harmonic of ST-OAM pulses are presented. The experiments also suggest a general ST-OAM nonlinearity, analogous to the orbital angular momentum of conventional light.

Presentation Details:

In this study, we use a rotating microcavity to control dissipative cur-solitons in a non-reciprocal manner. The nonreciprocal control is achieved by the Sagnac-Fizeau optical drag effect, in which light traveling in the direction of rotation of the resonator and light traveling in the opposite direction generate different soliton states. This result provides a promising path toward soliton-based optical isolators and one-way soliton communications.

Presentation Details:

In this paper, we theoretically study the generation of breathing dark pulses and Raman Kerr combs affected by induced Raman scattering and higher-order dispersion in silicon microcavities. Dark pulses exist only in microcavities with relatively large FSR compared to the Raman gain linewidth. The dark pulses induced by higher-order dispersion depend mainly on the amplitude and sign of the third-order dispersion coefficient, and their characteristics are also affected by the Raman-assisted four-wave mixing process. Knowledge of their existence will help us better understand the instabilities associated with Raman Kerr comb formation in microcavities exhibiting normal dispersion and avoid these instabilities for practical applications. Furthermore, broadband MIR microcombs generated via dispersive waves allow greater freedom in the fabrication of resonators and the acquisition of frequency combs on platforms where normal dispersion is dominant.

Presentation Details:

Lithium niobate (LN) has a large second- and third-order nonlinear optical coefficient and has been applied to various applications. However, the interaction between the Raman effect and other nonlinear optical effects in LN has not been well studied. In this paper, we evaluate the Raman effect in LN-based microcavities. We also generate optical Kercombs generated by nonlinear optical effects and evaluate the effect of the Raman effect on the generation of optical Kercombs.

Presentation Details:

We have proposed a photonic crystal laser (or photonic crystal surface emitting laser (PCSEL)) that has gain and loss sections arranged in two dimensions, with the loss section consisting of a saturable absorber, which enables short-pulse operation with high peak power (tens to hundreds of watts or more) at low cost and compactness, which is difficult with conventional semiconductor lasers. PCSEL)) was proposed. The gain and loss behaviors of the PCSEL were analyzed and designed considering the interaction between carriers and photons, and the structure that enables stable high peak-power short-pulse operation was demonstrated in practice.

Presentation Details:

Turnkey solitons, which can generate a soliton comb simply by applying an electric current, caused a great sensation when they were reported in Nature last year. By directly coupling a microcavity to a semiconductor laser and inducing self-injection locking, the laser is automatically redetuned, eliminating the need for complex mechanisms to control the wavelength of the laser. By combining a semiconductor laser and a silicon nitride resonator on a single substrate, the paper succeeds in further integrating turnkey solitons, bringing them much closer to practical application as multi-wavelength light sources.

Presentation Details:

Optical frequency combs using WGM microcavities have great potential for obtaining high spectral and energy efficiency in WDM transmission systems. However, communication applications of silica microspheres have been little studied. In this paper, we numerically study and optimize a 200 GHz optical frequency comb using silica microspheres and simulate its implementation in a 4-channel WDM transmission system.

Presentation Details:

Polarization control is a very important technology and has many possible applications. However, existing polarization optics can only manipulate polarization in a single transverse plane. In this paper, we propose a new metasurface that is independent of the incident polarization and gives arbitrary polarization response along the direction of propagation. This technique allows greater freedom in the design of metasurfaces and may expand the use of metasurfaces in more situations.

Presentation Details:

Fabrication of optical devices using liquids has attracted much attention as an attractive research area. Frequency tuning of such optical devices by reconfigurable shape control has been considered difficult due to the inherent properties of liquids. In this paper, we fabricate a WGM microlaser composed entirely of liquid on the surface of an aqueous solution using an ink-jet method and control the surface tension between the aqueous solution and the WGM microlaser using a surfactant, thereby successfully tuning the frequency of the lasing while keeping the shape reconfigurable. This technique was also used for sensing water-soluble organic compounds. This result is expected to be applied to fluid sensing and biosensing at the microscopic level.

Presentation Details:

Quantum computers are capable of performing certain calculations that are considered too unwieldy for classical computers. Boson sampling is one such computation, which in this study was performed by inputting 50 unidentifiable single-mode squeezed states into a 100-mode ultra-low-loss interferometer with full connectivity and random matrices, and sampling them using 100 high-efficiency single photon detectors. The dimension of the output state space is 10^30 and the sampling rate is 10^14 faster than using a state-of-the-art supercomputer.

Presentation Details:

Non-elmitic systems with Exceptional Points (EPO) have the potential to induce many unique phenomena in a variety of fields ranging from photonics, acoustics, optics, and electronics to atomic physics. In this paper, we introduce a non-Hermite system with coupled optical parametric oscillators (OPOs) and show its advantages compared to conventional non-Hermite systems that rely on laser gain and loss. In particular, we show the spectral parity symmetry breaking due to two coupled OPOs and the EP between their degenerate and non-degenerate operation.

Presentation Details:

A Brillouin laser is generated by induced Brillouin scattering in a micro optical resonator, and a dissipative Kerr soliton is generated in the same resonator using the Brillouin laser as the excitation light.
In this method, the input light is blue-detuning with respect to the resonance frequency and the Brillouin laser can be generated red-detuning, so a single soliton can be accessed with a simple wavelength sweep by the laser piezo. In addition, due to the ultra-narrow linewidth and low noise characteristics of the generated Brillouin laser, the observed solitons exhibit narrow comb lines and stable repetition rates.

Presentation Details:

Better performance in terms of data rate, power consumption, bandwidth, etc. is expected for 5th generation (5G) wireless access networks, and passive optical networks (PONs) in 5G are no exception.
In this study, we demonstrate error-free simultaneous transmission of data and clock signals using an optical frequency comb generated by gain switching of a vertical cavity surface emitting laser (VCSEL). This is intended for application to next-generation wavelength division multiplexing passive optical network systems (WDM-PON). In future WDM-PONs, which require increased channel capacity and strict delay monitoring, the results of this study suggest that VCSEL-based optical frequency comb may be used as a light source that can realize simple and energy-efficient networks.

Presentation Details:

Soliton crystals composed of equally spaced time pulses are an effective means of achieving ultra-high repetition rates. In this paper, the generation of soliton crystals in the presence of nonlinear mode coupling is investigated. It is shown that perfect soliton crystals can be realized reliably under the conditions of appropriate wave vector mismatch and nonlinear coupling coefficient.

Presentation Details:

In this study, a novel fiber-chip edge coupler approach with large mode sizes is proposed for silicon photonic thin-wire waveguides. The edge coupler structure is a multiple structure consisting of multiple silicon nitride layers embedded in a SiO2 upper cladding, a curved waveguide, and two spot size converter (SSC) sections. The edge coupler was designed for SMF-28 fiber with a mode field diameter (MFD) of 8.2 μm at a wavelength of 1550 nm and an overall coupling ratio of 90%.

Nature 591, 54-60 (2021)
J. M. Arrazola, V. Bergholm, K. Brádler, T. R. Bromley, M. J. Collins, I. Dhand, A. Fumagalli, T. Gerrits, A. Goussev, L. G. Helt, J. Hundal, T. Isacsson, R. B. Israel, J. Izaac, S. Jahangiri, R. Janik, N. Killoran, S. P. Kumar, J. Lavoie, A. E. Lita, D. H. Mahler, M. Menotti, B. Morrison, S. W. Nam, L. Neuhaus, H. Y. Qi, N. Quesada, A. Repingon, K. K. Sabapathy, M. Schuld, D. Su, J. Swinarton, A. Száva, K. Tan, P. Tan, V. D. Vaidya, Z. Vernon, Z. Zabaneh & Y. Zhang

Presentation Details:

The move toward practical quantum computing has led to a proliferation of programmable machines for executing quantum algorithms. In this paper, we present a system that uses integrated nanophotonics technology to execute multiphoton quantum circuits.

Presentation Details:

When a soliton comb generated on a micro optical resonator is detected by a photodetector, an RF signal of tens to hundreds of GHz can be generated depending on the repetition rate. Such RF signals show phase noise characteristics superior to those of signal generators, and are expected to be a next-generation RF signal source. In this paper, the factors of the phase noise are clarified by numerical calculations and empirical experiments in order to achieve higher performance.

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What is Journal Club?
This is an open lecture series held in Tanabe Photonic Structures Laboratory. Students who are graduate students or above will survey papers related to optics and related technologies such as photonics, materials, bioscience, etc., and explain them in an easy-to-understand manner.

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Attendance is free, regardless of whether you are inside or outside of the university. The seminar will be held periodically, so if you are interested in any of the topics, please feel free to attend. No notice is required to attend, but we will prepare materials if you contact us in advance.

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