Silicon Photonic Microresonator-Based High-Resolution Line-by-Line Pulse Shaping

Optical pulse shaping stands as a formidable technique in ultrafast optics, radio-frequency photonics, and quantum communications. While existing systems rely on bulk optics or integrated platforms with planar waveguide sections for spatial dispersion, they face limitations in achieving finer (few- or sub-GHz) spectrum control. These methods either demand considerable space or suffer from pronounced phase errors and optical losses when assembled to achieve fine resolution. Addressing these challenges, we present a foundry-fabricated six-channel silicon photonic shaper using microresonator filter banks with inline phase control and high spectral resolution. Leveraging existing comb-based spectroscopic techniques, we devise a novel system to mitigate thermal crosstalk and enable the versatile use of our on-chip shaper. Our results demonstrate the shaper's ability to phase-compensate six comb lines at tunable channel spacings of 3, 4, and 5 GHz. Specifically, at a 3 GHz channel spacing, we showcase the generation of arbitrary waveforms in the time domain. This scalable design and control scheme holds promise in meeting future demands for high-precision spectral shaping capabilities.Comment: 21 pages, 12 figure

Myomectomy at the Time of Cesarean Section: A Prospective Multicentre Study

Objectives: To assess the safety and efficacy of myomectomy during cesarean section. Methods : The study design was a prospective multicentre study done in three tertiary care hospitals in Dhaka city. The subject were 30 pregnant women underwent elective or emergency myomectomy during cesarean section. All cesarean section myomectomy were performed by consultant. Intra-operative and post-operative complications such as change in haematocrit, length of operation, blood loss were estimated. Length of hospital stay was also recorded. Results : 50 Fibroid of various sizes (2-6cm) were removed from 30 women. Fibroid were on the anterior uterine wall with most being subserous and intramural. Four patients had one unit of whole blood transfusion in post-operative period. No hysterectomy was done at the time of cesarean section. There was no significant frequency of blood transfusion; incidence of post- operative fever and duration of operation. The mean duration of post operative hospital study was 7.3±1.2 days. Two patients subsequently became pregnant, were also underwent repeated cesarean section in the study period. Conclusion : In selected cases myomectomy during cesarean section does not appear to result in an increased risk of intrapartum or short-term postpartum morbidity if performed by an experienced practitioner. Cesarean myomectomy is a safe surgical options with no significant complications. Keywords : Cesarean section; myomectomy; uterine myoma. DOI: http://dx.doi.org/10.3329/bsmmuj.v4i2.8639 BSMMU J 2011; 4(2):102-10

Myomectomy at the Time of Cesarean Section: A Prospective Multicentre Study

Objectives: To assess the safety and efficacy of myomectomy during cesarean section. Methods : The study design was a prospective multicentre study done in three tertiary care hospitals in Dhaka city. The subject were 30 pregnant women underwent elective or emergency myomectomy during cesarean section. All cesarean section myomectomy were performed by consultant. Intra-operative and post-operative complications such as change in haematocrit, length of operation, blood loss were estimated. Length of hospital stay was also recorded. Results : 50 Fibroid of various sizes (2-6cm) were removed from 30 women. Fibroid were on the anterior uterine wall with most being subserous and intramural. Four patients had one unit of whole blood transfusion in post-operative period. No hysterectomy was done at the time of cesarean section. There was no significant frequency of blood transfusion; incidence of post- operative fever and duration of operation. The mean duration of post operative hospital study was 7.3±1.2 days. Two patients subsequently became pregnant, were also underwent repeated cesarean section in the study period. Conclusion : In selected cases myomectomy during cesarean section does not appear to result in an increased risk of intrapartum or short-term postpartum morbidity if performed by an experienced practitioner. Cesarean myomectomy is a safe surgical options with no significant complications. Keywords : Cesarean section; myomectomy; uterine myoma. DOI: http://dx.doi.org/10.3329/bsmmuj.v4i2.8639 BSMMU J 2011; 4(2):102-10

Fine-Resolution Silicon Photonic Wavelength-Selective Switch Using Hybrid Multimode Racetrack Resonators

In this work, we describe a procedure for synthesizing racetrack resonators with large quality factors and apply it to realize a multi-channel wavelength-selective switch (WSS) on a silicon photonic chip. We first determine the contribution of each component primitive to propagation loss in a racetrack resonator and use this data to develop a model for the frequency response of arbitrary order, coupled-racetrack channel dropping filters. We design second-order racetrack filters based on this model and cascade multiple such filters to form a 1x7 WSS. We find good agreement between our model and device performance with second-order racetrack that have ~1 dB of drop-port loss, ~2 GHz FWHM linewidth, and low optical crosstalk due to the quick filter roll-off of ~ 5.3 dB/GHz. Using a control algorithm, we show three-channel operation of our WSS with a channel spacing of only 10 GHz. Owing to the high quality factor and quick roll-off of our filter design, adjacent channel crosstalk is measured to be <-25 dB for channels spaced on a 10 GHz grid. As a further demonstration, we use five of seven WSS channels to perform a demultiplexing operation on both an 8 GHz and a 10 GHz grid. These results suggest that a low-loss WSS with fine channel resolution can be realized in a scalable manner using the silicon photonics platform

Vernier Microcombs for Integrated Optical Atomic Clocks

CMOS-compatible Kerr microcombs have drawn substantial interest as mass-manufacturable, compact alternatives to bulk frequency combs. This could enable deployment of many comb-reliant applications previously confined to laboratories. Particularly enticing is the prospect of microcombs performing optical frequency division in compact optical atomic clocks. Unfortunately, it is difficult to meet the self-referencing requirement of microcombs in these systems due to the $\sim$THz repetition rates typically required for octave-spanning comb generation. Additionally, it is challenging to spectrally engineer a microcomb system to align a comb mode with an atomic clock transition with sufficient signal-to-noise ratio. Here, we adopt a Vernier dual-microcomb scheme for optical frequency division of a stabilized ultranarrow-linewidth continuous-wave laser at 871 nm to a $\sim$235 MHz output frequency. In addition to enabling measurement of the comb repetition rates, this scheme brings the freedom to pick comb lines from either or both of the combs. We exploit this flexibility to shift an ultra-high-frequency ($\sim$100 GHz) carrier-envelope offset beat down to frequencies where detection is possible and to place a comb line close to the 871 nm laser - tuned so that if frequency-doubled it would fall close to the clock transition in $^{171}$Yb$^+$. Moreover, we introduce a novel scheme which suppresses frequency noise arising from interferometric phase fluctuations in our dual-comb system and reduces the frequency instability down to our measurement limit. Our dual-comb system can potentially combine with an integrated ion trap toward future chip-scale optical atomic clocks

Vernier microcombs for high-frequency carrier envelope offset and repetition rate detection

Recent developments in Kerr microcombs may pave the way to a future with fully stabilized ultralow size, weight, and power consumption (SWaP) frequency combs. Nevertheless, Kerr microcombs are still hindered by a band-width/repetition rate trade-off. That is, the octave bandwidth needed for self-referencing is typically realized only with similar to THz repetition rates beyond the range of standard commercial photodetectors. The carrier envelope offset fre-quency fCEO is often likewise too high for detection. Dual-comb techniques for the measurement of THz repetition rates have made exciting progress, but the fCEO detection problem remains largely unaddressed. In this work, utilizing a Vernier dual-comb configuration, we demonstrate simultaneous detection of the electronically divided similar to 900 GHz rep-etition rate and similar to 97 GHz carrier envelope offset frequency of an octave-spanning microcomb. This, in turn, could help usher optical atomic clocks, low-noise microwave generators, and optical frequency synthesizers into various real-world applications.Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article\u27s title, journal citation, and DOI

Detection of harmful food additives using highly sensitive photonic crystal fiber

This paper presents three different structures of index guided hexagonal shaped Hollow Core Photonic Crystal Fiber (HC-PCF) specially designed for sensing harmful food additives like Saccharin, Sorbitol and Butyl Acetate. The proposed PCFs have three distinct combinations of hexagonal and/or circular airholes at the innermost cladding layer and in the core region. A comparative study among the proposed structures reveals that the introduction of the hexagonal airholes at the innermost cladding layer increases the sensitivity. Also, the addition of the large circular airholes at the outermost layer reduces the confinement loss in all three structures. The diameters of the airholes of the innermost and outermost layer of the cladding region are gradually varied to optimize the PCFs. The numerical inquiry reveals that the optimized best structure shows relative sensitivity of 88.75%, 87.37% and 86.72% for Saccharin, Sorbitol, and Butyl Acetate respectively at the operating wavelength of 1.33 μm. The performances of the proposed structures are also investigated using Ethanol as the sensed sample for the purpose of comparison with previously reported works. The comparison shows that the introduced fibers outperform most of the recent works. Numerical analyses of the proposed structures are conducted using Full Vectorial Finite Element Method (FV-FEM). Keywords: Photonic crystal Fiber, Food additives, Sensitivity, Confinement los

Silicon Photonic Microresonator-Based High-Resolution Line-by-Line Pulse Shaping

Optical pulse shaping stands as a formidable technique in ultrafast optics, radio-frequency photonics, and quantum communications. While existing systems rely on bulk optics or integrated platforms with planar waveguide sections for spatial dispersion, they face limitations in achieving finer (few- or sub-GHz) spectrum control. These methods either demand considerable space or suffer from pronounced phase errors and optical losses when assembled to achieve fine resolution. Addressing these challenges, we present a foundry-fabricated six-channel silicon photonic shaper using microresonator filter banks with inline phase control and high spectral resolution. Leveraging existing comb-based spectroscopic techniques, we devise a novel system to mitigate thermal crosstalk and enable the versatile use of our on-chip shaper. Our results demonstrate the shaper's ability to phase-compensate six comb lines at tunable channel spacings of 3, 4, and 5 GHz. Specifically, at a 3 GHz channel spacing, we showcase the generation of arbitrary waveforms in the time domain. This scalable design and control scheme holds promise in meeting future demands for high-precision spectral shaping capabilities

Vernier Frequency Combs for Stabilization of RF/Optical Links

We utilize the Vernier effect to partially stabilize a pair of high repetition rate, octave-spanning Kerr solitons in silicon nitride microrings fabricated on the same wafer

CMOS photonic integrated source of ultrabroadband polarization-entangled photons

We showcase a fully on-chip CMOS-fabricated silicon photonic integrated circuit employing a bidirectionally pumped microring and polarization splitter-rotators tailored for the generation of ultrabroadband ($>$9 THz), high-fidelity (90-98%) polarization-entangled photons. Spanning the optical C+L-band and producing over 116 frequency-bin pairs on a 38.4 GHz-spaced grid, this source is ideal for flex-grid wavelength-multiplexed entanglement distribution in multiuser networks