20 research outputs found
Electro-optic comb based real time ultra-high sensitivity phase noise measurement system for high frequency microwaves
Recent progress in ultra low phase noise microwave generation indispensably depends on ultra low phase noise characterization systems. However, achieving high sensitivity currently relies on time consuming averaging via cross correlation, which sometimes even underestimates phase noise because of residual correlations. Moreover, extending high sensitivity phase noise measurements to microwaves beyond 10 GHz is very difficult because of the lack of suitable high frequency microwave components. In this work, we introduce a delayed self-heterodyne method in conjunction with sensitivity enhancement via the use of higher order comb modes from an electro-optic comb for ultra-high sensitivity phase noise measurements. The method obviates the need for any high frequency RF components and has a frequency measurement range limited only by the bandwidth (100 GHz) of current electro-optic modulators. The estimated noise floor is as low as −133 dBc/Hz, −155 dBc/Hz, −170 dBc/Hz and −171 dBc/Hz without cross correlation at 1 kHz, 10 kHz, 100 kHz and 1 MHz Fourier offset frequency for a 10 GHz carrier, respectively. Moreover, since no cross correlation is necessary, RF oscillator phase noise can be directly suppressed via feedback up to 100 kHz frequency offset
A photonic frequency discriminator based on a two wavelength delayed self-heterodyne interferometer for low phase noise tunable micro/mm wave synthesis
Low phase noise frequency synthesizers are of paramount interest in many areas of micro-mm wave technology, encompassing for example advanced wireless communication, radar, radio-astronomy, and precision instrumentation. Although this broad research field is not bereft of methods for the generation of either low phase noise micro- or mm waves, no universal system applicable to low phase noise generation for micro and mm waves has yet been demonstrated. Here we propose a new photonic frequency discriminator based on a two wavelength delayed self-heterodyne interferometer which is compatible with such an objective. The photonic frequency discriminator can be a reference both for micro and mm waves to lower their phase noise. As a proof-of-concept, we demonstrate a low phase noise tunable OEO (6–18 GHz) and locking of a heterodyne beat between two cw lasers (10–400 GHz) with low relative phase noise. The required components for the photonic frequency discriminator are off-the-shelf and can be readily assembled. We believe this new type of photonic frequency discriminator will enable a new generation of universal precision tunable sources for the X, K, V, W and mm-bands and beyond
Stepped-Frequency THz-wave Signal Generation From a Kerr Microresonator Soliton Comb
Optically generated terahertz (THz) oscillators have garnered considerable
attention in recent years due to their potential for wide tunability and low
phase noise. Here, for the first time, a dissipative Kerr microresonator
soliton comb (DKS), which is inherently in a low noise state, is utilized to
produce a stepped-frequency THz signal ( 280 GHz). The frequency of
one comb mode from a DKS is scanned through an optical-recirculating
frequency-shifting loop (ORFSL) which induces a predetermined frequency step
onto the carrier frequency. The scanned signal is subsequently heterodyned with
an adjacent comb mode, generating a THz signal in a frequency range that is
determined by the repetition frequency of the DKS. The proposed method is
proved by proof-of-concept experiments with MHz level electronics, showing a
bandwidth of 4.15 GHz with a frequency step of 83 MHz and a period of 16
s
Solving multi-armed bandit problems using a chaotic microresonator comb
The Multi-Armed Bandit (MAB) problem, foundational to reinforcement
learning-based decision-making, addresses the challenge of maximizing rewards
amidst multiple uncertain choices. While algorithmic solutions are effective,
their computational efficiency diminishes with increasing problem complexity.
Photonic accelerators, leveraging temporal and spatial-temporal chaos, have
emerged as promising alternatives. However, despite these advancements, current
approaches either compromise computation speed or amplify system complexity. In
this paper, we introduce a chaotic microresonator frequency comb (chaos comb)
to tackle the MAB problem, where each comb mode is assigned to a slot machine.
Through a proof-of-concept experiment, we employ 44 comb modes to address an
MAB with 44 slot machines, demonstrating performance competitive with both
conventional software algorithms and other photonic methods. Further, the
scalability of decision making is explored with up to 512 slot machines using
experimentally obtained temporal chaos in different time slots. Power-law
scalability is achieved with an exponent of 0.96, outperforming conventional
software-based algorithms. Moreover, we find that a numerically calculated
chaos comb accurately reproduces experimental results, paving the way for
discussions on strategies to increase the number of slot machines
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Low noise electro-optic comb generation by fully stabilizing to a mode-locked fiber comb.
A fully stabilized EO comb is demonstrated by phase locking the two degrees of freedom of an EO comb to a low noise mode-locked fiber comb. Division/magnification of residual phase noise of locked beats is observed by measuring an out-of-loop beat. By phase locking the 200 th harmonics of the EO comb and a driving cw frequency to a fiber comb, a record low phase noise EO comb across +/- 200 harmonics (from 1544.8 nm to 1577.3 nm) is demonstrated
Low phase noise THz generation from a fiber-referenced Kerr microresonator soliton comb
THz oscillators generated via frequency-multiplication of microwaves are facing difficulty in achieving low phase noise. Photonics-based techniques, in which optical two tones are translated to a THz wave through opto-electronic conversion, are promising if the relative phase noise between the two tones is well suppressed. Here, a THz (≈560 GHz) wave with a low phase noise is provided by a frequency-stabilized, dissipative Kerr microresonator soliton comb. The repetition frequency of the comb is stabilized to a long fiber in a two-wavelength delayed self-heterodyne interferometer, significantly reducing the phase noise of the THz wave. A measurement technique to characterize the phase noise of the THz wave beyond the limit of a frequency-multiplied microwave is also demonstrated, showing the superior phase noise of the THz wave to any other photonic THz oscillators (>300 GHz)
Low phase noise THz generation from a fiber-referenced Kerr microresonator soliton comb
THz oscillators generated via frequency-multiplication of microwaves are
facing difficulty in achieving low phase noise. Photonics-based techniques, in
which optical two tones are translated to a THz wave through opto-electronic
conversion, are promising if the relative phase noise between the two tones is
well suppressed. Here, a THz ( 560 GHz) wave with an unprecedented
phase noise is provided by a frequency-stabilized, dissipative Kerr
microresonator soliton comb. The repetition frequency of the comb is stabilized
to a long fiber in a two-wavelength delayed self-heterodyne interferometer,
significantly reducing the phase noise of the THz wave. A new measurement
technique to characterize the phase noise of the THz wave beyond the limit of a
frequency-multiplied microwave is also demonstrated, showing the superior phase
noise of the THz wave to any other THz oscillators (> 300 GHz)
Terahertz wireless communication at 560-GHz band using Kerr micro-resonator soliton comb
Terahertz (THz) waves have attracted attention as carrier waves for
next-generation wireless communications (6G). Electronic THz emitters are
widely used in current mobile communications; however, they may face technical
limitations in 6G with upper-frequency limits. We demonstrate wireless
communication in a 560-GHz band by using a photonic THz emitter based on
photomixing of a 560-GHz-spacing soliton microcomb in a uni-travelling carrier
photodiode together with a THz receiver of Schottky barrier diode. The on-off
keying data transfer with 2-Gbit/s achieves a Q-factor of 3.4, thus, satisfying
the limit of forward error correction.Comment: 17 pages, 4 figur