We explore the spatiotemporal evolution of dispersion-induced pulse broadening in water. The Lorentz–Lorenz function is utilized to establish the relationship between the refractive index and the wavelength of the incident laser. Therefore, the dispersion coefficients are derived. Using the Schrödinger equation, we model the propagation of laser pulses over a 1-m optical length in water. Subsequently, the spatiotemporal evolution is obtained by the relationship between the spatial and temporal components of the light field. The results indicate that lasers with shorter central wavelengths and shorter pulse durations experience greater pulse broadening and significant bandwidth reduction. This methodology demonstrates the potential for enhancing underwater optical communication, representing a noteworthy advancement in both scientific research and practical applications.
We present a simple and stable quantitative phase imaging technique via Fresnel biprism-based digital holographic microscopy. A Fresnel biprism is used to divide the incoming beam and generate self-referencing common-path configuration. So, high contrast hologram is produced in overlapping area. To evaluate the performance of Fresnel biprism with different refringence angles, the system magnification and length are discussed in detail. In addition, different sources of illumination, such as laser and LED, are used in proposed system for studying the feasibility of quantitative phase imaging. The temporal stability of system is also illustrated by comparing with the Mach-Zehnder-based off-axis digital holographic setup. It is shown that the proposed scheme has sub-nanometer temporal stability (~0.109𝑛𝑚) due to the common-path geometry. The experiments on micro-lens array, biological cell and water droplet are reported demonstrating its application both for static and dynamic samples. The refractive index measurement results of polyester fiber also further demonstrate the effectiveness of the proposed system.
We present a simple and effective method for dual-wavelength phase imaging in Lensless Reflection Digital Holographic Microscopy (LRDHM). A filter is inserted between beam splitter and mirror in LRDHM. By adjusting the filter and mirror, the propagation directions of two reference beams of different wavelengths can be separated, and thus two off axis holograms with different fringe directions are simultaneously captured by a monochrome camera. Our scheme is available for real-time dual-wavelength phase imaging but requires minimum optical element and system modification for LRDHM. A series of simulations on wavefront interference analysis for using a filter is discussed in detail. We demonstrate the validity of proposed method with a step target.
A single-shot dual-wavelength lensless digital holography based on a dichroic mirror is presented to achieve quantitative phase imaging. The lensless digital holography is designed by a wavefront division transmission configuration with only a plane mirror and a beam splitter. By merely adding a dichroic mirror between plane mirror and beam splitter in lensless transmission digital holography, the propagation direction of two reference waves for different wavelengths can be adjusted separately by dichroic mirror and plane mirror. Therefore, a multiplexed hologram with different fringe directions for two wavelengths can be simultaneously obtained. Our technique is capable of real-time wavelength-multiplexing with minimum optical element and system modification.
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