We present the first direct carrier-envelope-offset (CEO) frequency detection of a modelocked laser based on supercontinuum generation (SCG) in a CMOS-compatible silicon nitride (Si(3)N(4)) ...waveguide. With a coherent supercontinuum spanning more than 1.5 octaves from visible to beyond telecommunication wavelengths, we achieve self-referencing of SESAM modelocked diode-pumped Yb:CALGO lasers using standard f-to-2f interferometry. We directly obtain without amplification strong CEO beat signals for both a 100-MHz and 1-GHz pulse repetition rate laser. High signal-to-noise ratios (SNR) of > 25 dB and even > 30 dB have been generated with only 30 pJ and 36 pJ of coupled pulse energy from the megahertz and gigahertz laser respectively. We compare these results to self-referencing using a commercial photonic crystal fiber and find that the required peak power for CEO beat detection with a comparable SNR is lowered by more than an order of magnitude when using a Si(3)N(4) waveguide.
Ultrafast semiconductor disk lasers (SDLs) passively modelocked using semiconductor saturable absorbers mirrors (SESAMs) generate optical frequency combs (OFCs) with gigahertz line spacings - a ...regime where solid-state and fiber lasers struggle with geometrical and Q-switching limitations. We stabilized both the frequency comb spacing and the offset without any additional external optical amplification or pulse compression. The overall noise performance is competitive with other gigahertz OFCs. A SESAM-modelocked vertical external-cavity surface-emitting laser (VECSEL) at a center wavelength around 1 µm generates 122-fs pulses with 160 mW average output power and we only needed 17-pJ pulse energy coupled into a silicon nitride (Si
N
) waveguide for supercontinuum generation (SCG) and OFC offset stabilization.
We demonstrate an all-optical tunable pulse delay scheme that utilizes the power-dependent variation of the refractive index that accompanies stimulated Raman scattering in an optical fiber. Using ...this technique, we delay 430-fs pulses by up to 85% of a pulse width. The ability to accommodate the bandwidth of pulses shorter than 1 ps in a fiber-based system makes this technique potentially viable for producing controllable delays in ultra-high bandwidth telecommunication systems.
Retrieving chlorophyll-a concentration (Chla) from remote-sensing data is especially challenging in coastal regions because of the presence of other co-dominant optically significant constituents ...(OSCs). In this study, we characterize bio-optical variability at a fixed coastal time series station in the South Brazil Bight (SBB), the ANTARES-Ubatuba site (São Paulo, Brazil) from radiometric measurements and water sample analyses, and evaluate the performance of ocean colour (OC) algorithms for Chla retrieval. In situ Chla and the spectral absorption of phytoplankton (a
ph
), detritus, and coloured dissolved organic matter (CDOM), as well as the above-water remote-sensing reflectance (R
rs
) were obtained from 2004 to 2019 at a quasi-monthly sampling frequency. Chla exhibited high variability, with a standard deviation twice as large as the mean (1.0 ± 1.83 mg m
−3
), and values ranging from 0.18 mg m
−3
up to 18.09 mg m
−3
during episodic bloom events. CDOM was the dominant OSC contributing to the absorption coefficient at 443 nm all-year round, suggesting the influence of continental sources, even though the station is located at the external limit of the inner shelf (40 m). Two optical water types were defined: one composed mainly of 'blue' waters with lower concentrations of the OSCs and another of 'green' waters with higher concentrations of OSCs. Despite the CDOM spectral dominance, the empirical OCx performed reasonably well with a positive bias for both in situ (17-25%) and satellite (25-31%) Chla retrievals. The performance was slightly better using the 3-band OC3 algorithm by selecting the best band ratio with lower influence of CDM (CDOM + detritus) absorption (R
rs
(490/555)). The main sources of uncertainty were caused by higher CDM proportions and phytoplankton-specific absorption, yielding positive biases on the OC3 retrievals. The results suggest that standard satellite products of Chla can be used (with some caution) to monitor and study the dynamics of the phytoplankton biomass within the region, knowing the expected uncertainties.
We use light from a visible laser diode to directly tune silicon-on-chip microresonators by thermo-optical effect. We show that this direct tuning is local, non invasive and has a much smaller time ...constant than global temperature tuning methods. Such an approach could prove to be highly effective for Kerr comb generation in microresonators pumped by quantum cascade lasers, which cannot be easily tuned to achieve comb generation and soliton-mode locked states.
This letter presents an optically controlled, continuously tunable, dispersionless optical delay element in fiber based on a selective wavelength converter using a periodically poled lithium-niobate ...waveguide with two-pump configuration, dispersion-compensated fiber, and a dispersion compensator. Optical phase information is preserved in this technique, and there is no fundamental limitation on pulsewidth or bit rate. A Continuous optical delay up to 44-ns is shown for 10-Gb/s nonreturn-to-zero applications, which is equal to a 440-bit slot
The measured dispersion of a low-loss, hollow-core photonic band-gap fiber is anomalous throughout most of the transmission band, and its variation with wavelength is large compared with that of a ...conventional step-index fiber. For an air-filled fiber, femtosecond self-frequency-shifted fundamental solitons with peak powers greater than 2 megawatts can be supported. For Xe-filled fibers, nonfrequency-shifted temporal solitons with peak powers greater than 5.5 megawatts can be generated, representing an increase in the power that can be propagated in an optical fiber of two orders of magnitude. The results demonstrate a unique capability to deliver high-power pulses in a single spatial mode over distances exceeding 200 meters.
By exploiting the broad region of anomalous group-velocity dispersion (GVD) and the large e.ective nonlinearity of photonic nanowires, we demonstrate soliton-e.ect self-compression of 70-fs pulses ...down to 6.8 fs. Under suitable conditions, simulations predict that self-compression down to single-cycle duration is possible.
We investigate theoretically and experimentally the process of supercontinuum generated in sub-wavelength waveguides. We observe experimentally that supercontinuum generated in these photonic ...nanowires is increasingly blue-shifted from the pump wavelength for decreasing minimum core diameters. We also find the spectral features are sensitive to the specific nanowire profile. Numerical simulations using the nonlinear envelope equation show that accurate modeling requires consideration of the nonlinearity and full dispersion along the entire nanowire profile as well as a wavelength dependent loss. Specifically, the blue-shifting is found to result from an increasing loss for wavelengths larger than the core diameter.
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