Satya Pratap Singh

Dual colour cw mode-locking through soft aperture based on second order cascaded nonlinearity

Large nonlinear phase shift achieved by exploiting intracavity second order cascaded nonlinear process in a non-phasematched second harmonic generating crystal is transformed into amplitude modulation through soft aperturing the nonlinear cavity mode variation within the laser gain medium to mode-lock a Nd:YVO4 laser. The laser delivers stable dual wavelength cw mode-locked pulse train with pulse duration 10.3 ps and average power of 1.84 W and 255 mW at 1064 nm and 532 nm respectively for a pump power of 12 W. A comprehensive theoretical analysis finds the regime of self starting and stable cascaded second order mode-locking, inconformity with the experimental result.

Dispersion Engineered Capillary-Assisted Chalcogenide Optical Fiber Based Mid-IR Parametric Sources

We report the detailed theoretical investigations of a capillary-assisted chalcogenide optical fibers exhibiting three zero dispersion wavelengths and small magnitude of chromatic dispersion. The dispersion characteristics of the proposed fiber can be tailored externally by temperature when the air-capillary is infiltrated with suitable thermooptic liquids. This has led to design and development of thermally tunable broadband CW pumped optical parametric amplifier (OPA) in mid-IR region with bandwidth greater than 2000 nm. By considering the sixth-order dispersion parameter in the phase-matching condition, we have shown the temperature-dependent various phase-matching topologies which are only possible with different fiber structures as reported earlier. The key benefits of the proposed tunable OPA are the generation of new radiations of varying line widths.

Widely Tunable Intracavity Phasematched Cascaded Second-Order Interaction for the Generation of Multicolor Radiation

A theoretical and experimental study of all-solid-state barium borate (BBO)-based optical parametric oscillator with wide tunability from visible to near-infrared by means of intracavity second-order cascaded nonlinear interaction has been demonstrated for simultaneous generation of multicolor radiation. Radiations in the wavelength range of 600-661 nm in the visible and 892-1322 nm in the near-infrared range are generated by a combination of optical parametric oscillation and simultaneous second harmonic generation in BBO crystal. The effective third-order susceptibility is measured to be 885.18 pm2/V2, which is greater than intrinsic third-order susceptibility by one order of magnitude.

Dynamic gain aperture modelocking in picosecond regime based on cascaded second-order nonlinearity

The operation of a cascaded second-order mode-locked Nd:YVO4 laser has been investigated considering it as a soft-aperture Kerr lens type and using complex beam parameters. A self consistent complex beam propagation method is used to incorporate the effect of cascaded Kerr nonlinearity on radially varying gain aperturing. The analysis deduces a stable pulsewidth of ~9.5 ps which agrees well with the experimental value of 10.3 ps.

Sub-Wavelength Dual Capillaries-Assisted Chalcogenide Optical Fibers: Unusual Modal Properties in Mid-IR (2–5 μ m) Spectral Range

In this study, we apply the concept of sub-wavelength light confinement to achieve flat effective mode area (Aeff) characteristics over a wide wavelength range of 1400 nm in nano-sized dual capillary assisted chalcogenide core optical fibers. An unusual spectral behavior of Aeff is observed where the effective mode area increases, remains constant for a wide bandwidth, decreases and again increases with the increase in wavelength. The spectral region, in which this behavior is observed, can be tuned by varying the structural parameters of the fiber. Additionally, we noticed that the fiber exhibits four zero dispersion wavelengths for a particular polarization which suggests that sub-wavelength light localization can be an alternative solution for the dispersion engineering in order to attain multiple zero dispersion wavelengths. The fabrication tolerance of the dispersion profile has been found to fall within the current fabrication accuracies achievable. We believe that our findings might be useful in different applications such as light-matter interaction and spatial soliton propagation.

CW pumped, generation of narrow linewidth non-resonant mid-IR radiations in liquid filled single capillary assisted chalcogenide optical fibers

We report the generation of the non-resonant radiations (<;100 GHz FWHM) ranging from near-IR to mid-IR in capillary-assisted chalcogenide optical fibers with three zero dispersion wavelengths owing to the temperature dependent phase-matching topologies.

Interfacial delamination in glass-fiber/polymer-foam-core sandwich composites using singlemode–multimode–singlemode optical fiber sensors: Identification based on experimental investigation

Identification of interfacial delamination in the glass fiber/polymer-foam-core sandwich composites is difficult if the delamination does not propagate to the side surface of the specimen. However, these damages may eventually lead to compromising the sandwich composite structural component. A cost-effective novel embedded fiber optic sensor is being proposed in this manuscript, which works on the principle of multimode interference, to perform distributed sensing of interfacial delamination within the sandwich composites while in service. Even though this easy to use methodology has been used to identify interfacial delamination, this methodology can also be used for different other types of interfacial/interlaminar distributed strain sensing of samples under mechanical as well as thermal loads.

Pulse-Splitting and Pulse-Locking Dynamics in Multi-Mode Optical Fibers

We study the multimode propagation dynamics in a fiber, observe the pulse-splitting and pulse-locking marked by a significant portion of the LP01-mode pulse moving together with the LP02-mode pulse despite of significant walk-off between them.

Mid-IR multipeak and stepwise blueshifted dispersive wave generation in liquid-filled chalcogenide capillary optical fibers

We propose a new approach to produce a tunable supercontinuum source in the mid-IR range (2–5 μm) through liquid-filled chalcogenide capillary optical fibers. The presence of a single capillary at the center of the fiber core, filled with an appropriate thermo-optic liquid, facilitates the engineering of the dispersive wave (DW) dynamics. We show that a single fiber can exhibit both a single zero-dispersion wavelength (ZDW) and multiple ZDWs by varying the temperature that leads to the generation of highly tailored DWs. By a judicious choice of temperature distribution along the fiber length, discrete multipeaked DWs and continuously blueshifted DWs are generated in a single-fiber structure.

Sub-wavelength confinement in dual capillary assisted chalcogenide core optical fiber for Mid-IR Applications

The sub-wavelength confinement of electromagnetic field is exploited to attain unconventional, almost-flattened and tunable spectral behaviour of effective mode-area and multiple zero dispersion points in nano-sized dual air-capillary assisted chalcogenide optical fiber for mid-IR applications