Journal Club 2019 | Tanabe Photonic Structure Group

Journal Club

By fiscal year (April-December)

Fiscal Year 2019

Presentation Details:

Soliton generation using fibers and micro optical resonators is used in a wide range of fields. However, when an external light source is used, there are still issues in terms of coherence, control of mode spacing, and long-time operation. In this study, the optical Kerr effect is generated by using Brillouin scattering in the resonator. Using this method, the repetition rate can be varied from GHz to THz without changing the resonator length.

Laser & Photonics Review 13(2) - January 2019
Zachary L. Newman, Vincent Maurice, Tara Drake, Jordan R. Stone, Travis C. Briles, Daryl T. Spencer, Connor Fredrick, Qing Li, Daron Westly, B. R. Ilic, Boqiang Shen, Myoung-Gyun Suh, Ki Youl Yang, Cort Johnson, David M. S. Johnson, Leo Hollberg, Kerry J. Vahala, Kartik Srinivasan, Scott A. Diddams, John Kitching, Scott B. Papp, and Matthew T. Hummon

Presentation Details:

Optical atomic clocks have recently achieved ultra-high precision of more than 18 orders of magnitude, but their large size and the use of bulk packaging have prevented their widespread application. In this study, an optical atomic clock with stability close to 10^-13 was successfully fabricated by using two micro optical resonators made of silicon nitride and silica, generating a clock signal using a frequency-locked comb, and dividing the optical transition frequency in an Rb vapor cell.

Presentation Details:

A feasible method for integrating several silicon (Si) photonic devices with operating wavelengths separated by several hundred nanometers on a single This work demonstrates the integration of two photonic crystal This work demonstrates the integration of two photonic crystal nanocavity devices that exhibit ultrahigh quality factors (Q) and operate at the 1.31- and 1.55-µm bands. The two nanocavity patterns are deﬁned by electron beam lithography on the thick and thin substrate regions and are All dimensions of the fabricated 1.31-µm nanocavity are [1]15.5% smaller (1-1.31/1.55) than those of the 1.55-µm nanocavity; that is, they can be treated with the same photonic band diagram. exhibit an ultrahigh Q > 2.0×106 and enable fabrication of nanocavity-based Raman lasers for the 1.31/1.55-µm bands with sub-microwatt threshold.

Presentation Details:

DP-MZI is proposed as a method to integrate the main functions of a microcavity optical frequency comb into a single device.
This approach allows fceo and frep to be controlled in addition to generating stable DKS.
Experiments investigate the effects of pump frequency and power modulation via DP-MZI on fceo and frep, followed by a demonstration of the long-term stability of the micro-resonator soliton comb.
In addition, fiber referencing via TWDI greatly suppresses soliton com timing jitter.

Presentation Details:

Ultrashort pulses from fiber lasers are widely used in research and industry. While they have many advantages such as compactness and low cost, confining intense pulses within a fiber causes undesirable nonlinear effects. Here, we fabricated a fiber laser-based amplifier by using such nonlinear effects. The amplification results were spectrally wider than the gain bandwidth and achieved pulse widths of about 30 fs.

Presentation Details:

Optical spectroscopy is an important technology enabling optical analysis in a variety of disciplines and research areas. With the increasing demand for miniaturization and higher resolution as devices, achieving both of these goals has been a challenge. In this study, a Fourier transform spectrometer is fabricated using a waveguide structure based on LN-SiN as a material, and a high-resolution and compact spectrometer structure is verified in a wide wavelength range of 500 nm in the NIR region.

Presentation Details:

The realization of strong coupling between high-frequency phonons and light using resonators can be used for quantum state transfer, quantum memory, and quantum transformation. The realization of strong coupling between high-frequency phonons and light using resonators can be used for quantum state transfer, quantum memory, quantum transformation, etc. In addition, it is also a field that is attracting attention in fundamental physics research. However, it has been difficult to achieve a strongly coupled state in resonators with opportunity vibration modes above GHz.
In this study, we report the first strong coupling between light and high-frequency phonons using Brillouin scattering and silica rod resonators at 11 GHz.

Presentation Details:

In this paper, we proposed a structure to realize an all-optical digital multiplexer. The proposed structure had two inputs, one control and one output port. Using the control port, one can decide which input port can be connected to the output port. The proposed structure consisted of two nonlinear photonic crystal ring resonators, L-shaped and T-shaped, and a straight waveguide. Total footprint and maximum delay time of the proposed structure were 479 um^2 and 3 ps, respectively.

Presentation Details:

Dissipative Kerr solitons (DKS) are pulse trains produced by nonlinear optical effects in micro optical resonators, which are compatible with nonlinear optics and optical integration technologies. The dynamics of soliton crystals has not been well understood. In this study, we derived the stable region of the soliton crystal by solving LLE, and verified the change of the soliton crystal state by changing the detuning and power of the pump light. The results are expected to be applied to the generation of stable single solitons.

Presentation Details:

Silica optical fibers are indispensable in international telecommunications and IoT networks due to their ubiquity and low loss. In this study, single-mode and multimode silica optical fibers were fabricated by a 3D printing method for the first time. This method enables the design of fibers with geometries that are impossible with conventional optical fiber fabrication methods.

Presentation Details:

This paper reports on nonlinear filtering of optical pulse trains based on time-dissipative cur solitons in microcavities. Experimental results combined with analytical and numerical modeling show that soliton dynamics can store information about the physical state of the system longer than the energy conservation time of the cavity, thereby producing filter widths that can be an order of magnitude larger than the intrinsic linewidth of the cavity can be produced. Such nonlinear optical filtering has immediate applications in optical metrology and generation of ultrashort optical pulses with low timing jitter, and could open new avenues in microwave photonics.

Presentation Details:

The pulse width in solid-state ultrashort pulse lasers is limited by the oscillation bandwidth of the laser crystal. Therefore, efforts to expand the gain oscillation bandwidth have been made for about half a century.
Here, we report a new method of spectral broadening using induced Raman scattering, which significantly shortens the pulse width. Generally, spectral broadening using induced Raman scattering is based on the synchronous pumping method. In this study, the spectral broadening is achieved by utilizing the spectra of both the pulsed light source and Raman scattering. The laser is a Kerr lens mode synchronous laser using Yb:CALGO as the laser crystal, and the pulse width is shortened to 1/3 (22 fs) of the conventional pulse width as a result of spectrum expansion.

Presentation Details:

Random lasers have attracted attention as devices that can be raged without using a resonator structure. On the other hand, however, the randomness of the device makes it difficult to predict and control the device characteristics. In this study, we verified that by controlling the randomness of the photonic crystal structure, it is possible to control various characteristics of the laser, including its oscillation wavelength and number of modes.

Presentation Details:

Large-scale optical integrated circuits will also be very important for quantum information communications. However, silicon photonics and single-photon sources have often been studied independently of each other. The reason for this is the difference in materials, as the materials commonly used in silicon photonics cannot be used to make single-photon sources, and different materials are inevitably required.
In this presentation, we will introduce previous studies combining silicon photonics and single-photon sources, and describe the method employed by our research group and its advantages.

Presentation Details:

Abstract: Optical parametric processes enable the generation of coherent electromagnetic radiation at new wavelengths. This allows modulation over a wide range of wavelengths, and is expected to be used in a variety of applications ranging from spectroscopy to quantum information processing. However, existing tunable parametric light sources have drawbacks that limit their application. In this paper, we overcome these limitations by using magnesium fluoride crystalline micro optical resonators with ultra-high Q-values to fabricate a compact and power-efficient device that can generate a wide range of modulatable side-wave bands. Several different resonators with precisely designed dispersion profiles were investigated, and modulatable sidebands of several hundred nanometers were achieved for each resonator. In addition to observing modulation across optical octaves from 1,083 nm to 2,670 nm, a mid-infrared sideband was measured at 4,000 nm. The demonstrated device is expected to realize a low-cost light source that can be modulated over a wide range of wavelengths.

Presentation Details:

Ideally, optical modulators should be characterized by low loss, low drive voltage, wide bandwidth, high linearity, small footprint, and low manufacturing cost. Unfortunately, it has been difficult to achieve many of these characteristics simultaneously.
In this study, based on a hybrid integrated silicon and lithium niobate platform, a Mach-Zehnder modulator was fabricated to simultaneously satisfy the above-mentioned indices.
The performance evaluation demonstrated that the proposed device exhibits 2.5 dB insertion loss, a voltage-to-length product of 2.2 V cm in single-drive push-pull operation, high linearity, an EO bandwidth of at least 70 GHz, and modulation rates up to 112 Gbit/s.
With these results, the proposed platform offers new possibilities for future high-speed, energy-efficient, and cost-effective optical communication networks.

Presentation Details:

A WGM resonator fabricated with a laser active medium works as an efficient coherent light source. However, to achieve such a high output power, it is necessary to use an expensive laser source with a narrow linewidth, which is inappropriate for actual use. In this study, we report a WGM resonator that operates stably despite pumping with an inexpensive laser diode. We have succeeded in solving the conventional problems such as concerns about higher-order modes, oscillation direction, low output power, and stability.

Presentation Details:

We demonstrate a proof-of-concept saturable absorption based pulsewidth measurement (SAPM) by exploring the intensity dependent nonlinear We demonstrate a proof-of-concept saturable absorption based pulsewidth measurement (SAPM) by exploring the intensity dependent nonlinear transmission (i.e., saturable absorption) of low-dimensional material (LDM) carbon nanotubes. A minimum detectable pulse energy of 10 fJ with a Pav⋅ Ppk of The nanometer-level thickness and femtosecond-level decay time of LDMs allow ultrafast light The nanometer-level thickness and femtosecond-level decay time of LDMs allow ultrafast light interaction on a very small footprint, which potentially supports chip-scale characterization of ultrafast pulses with minimum distortion.

Presentation Details:

There are many different types of physical phenomena and principles that give rise to color. Optical absorption in selective spectra by dyes, dispersion and interference in micro- and nano-scale periodic structures are examples. In this study, we realize a new method for creating iridescent structural colors. To this end, new theoretical predictions and validations have been made using multilayer droplets, 3D polymers, and solid particles. We have shown that controllable structural colors can be designed at the microscale.

Presentation Details:

In order to accelerate information communication and information processing on chips, there is a need to introduce photonics technology into the electronic circuits that have been developed so far. The problem is the capacitance in the EO and OE conversion areas, which requires a large amount of charge, resulting in low conversion efficiency. In this study, photonic crystals were used to realize ultra-low capacitance. We have succeeded in fabricating an EO modulator that operates with the world's lowest energy and an amplifier-free photoreceiver. In addition, by combining these two elements on a single chip, we fabricated a femtoFarad-order OEO transistor and realized wavelength conversion, optical amplification, and optical switch with ultra-low power consumption.

Presentation Details:

We present a graphene photodetector for datacom applications based on a silicon photonic crystal defect waveguide. Additionally, it is utilized as a split-gate electrode to create a p-n junction. Additionally, it is utilized as a split-gate electrode to create a p-n junction in the vicinity of the optical absorption region. The photonic crystal defect waveguide allows for optimal photo-thermoelectric conversion of the occurring temperature profile in graphene into a photovoltage due to additional silicon The photonic crystal defect waveguide allows for optimal photo-thermoelectric conversion of the occurring temperature profile in graphene into a photovoltage due to additional silicon slabs on both sides of the waveguide, enhancing the device response as compared to a conventional slot waveguide design. Under a moderate bias of 0.4 V we obtain a photoconductive responsivity of 0.17 A/W.

Presentation Details:

Analog photonic links require high-fidelity, high-speed optical-to-electrical conversion for applications such as fiber wireless communications, synchronization in kilometer-scale facilities, and low-noise electronic signal generation. Non-linearity in photodetectors is a particularly troublesome problem, causing signal distortion and excessive noise in systems utilizing ultrashort optical pulses. Here we show that photodetectors designed for high power processing and high linearity can perform optical-to-electrical conversion of ultrashort optical pulses with unprecedented linearity over a wide photocurrent range.
This research has resulted in a significant performance improvement over state-of-the-art photodiodes and a significant increase in achievable microwave power.

Presentation Details:

MIXSELs (mode-locked integrated external cavity surface emitting lasers) are a relatively new type of semiconductor laser. The resonator is constructed by stacking gain and saturable absorption media, which are necessary for laser oscillation and mode-locking, on a single wafer. Despite the high fabrication cost, the laser can achieve repetition rates from 5 GHz to 100 GHz because the cavity length can be controlled by the number of layers, and the output power can be as high as several 100 mW.
In this study, a MIXSEL with a repetition rate of 2.7 GHz, a pulse width of 150 fs, a spectral width of 13 nm (FWHM), and an output power of 30 mW was fabricated using a method different from conventional manufacturing methods. In the presentation, we will explain the structure and mechanism of MIXSEL, compare it with VECSEL (vertical cavity surface emitting laser), and discuss its applications.

Presentation Details:

Optical frequency comb (microcomb) based on micro optical resonators using integrated photonics technology is a promising light source with a wide range of applications in metrology, communications, and sensing. In particular, ring resonators made of silicon nitride (Si3N4) have been widely used in recent years because they cover both integration and high nonlinearity.
In this study, a broadband microcomb over one octave with a wavelength of 767-1556 nm was generated by controlling the dispersion of silicon nitride resonators, using a 1064 nm wavelength laser as a pump. To tune the mode frequency of the microcomb, a chip containing 75 ring resonators of varying dimensions was designed. This single-chip frequency comb source allows access to all wavelengths from the near-infrared region to the telecommunications wavelength band, which is important for atomic spectroscopy.

Presentation Details:

Lithium niobate LN (LiNbO3) is well known as an optical material with high second-order nonlinearity. In particular, there is a long history of more than 25 years of research on LNs for combing by electro-optic effects. However, LNs cannot be grown on silica substrates, and it has been difficult to generate broadband combs due to their structural disadvantages.
In this study, we have achieved comb generation over a very wide wavelength range (1560nm-1640nm) by biasing a microwave voltage through a waveguide of LNs on a silica substrate. Furthermore, the width of the comb can be freely changed by varying the frequency of the bias voltage, and this technique can be applied to on-chip dual comb generation.

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Anyone can register.

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.

About auditing
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.

Announcement of the event
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