סמינר פרונטלי בית הספר להנדסת חשמל ומחשבים 29/10/2025
סמינר מחלקתי
Full name: Aron Peisakhov
Degree: MSc in Electro-Optical Engineering
Supervisor: Prof. Amiel A. Ishaaya Subject: Characterization of SBS suppression in optical fibers via spectral and temporal distribution: a pathway to scalable power transmission
Abstract:
Stimulated Brillouin scattering (SBS) is one of the most significant nonlinear effects that limit optical power transmission in fiber-based systems. This phenomenon imposes a fundamental constraint on the scalability of output power in narrow-linewidth, single-frequency fiber lasers and amplifiers. SBS arises due to the interaction between optical waves and acoustic phonons within the fiber medium, leading to backscattering of light and power loss, and potentially causing instability or even damage in high-power systems. As such, effective suppression of SBS is crucial for the advancement of high-power fiber-based technologies in fields such as telecommunications, directed energy systems, LIDAR, and material processing.
We present an experimental investigation into SBS suppression techniques based on a hybrid temporal and spectral modulation approach. Specifically, we study the behavior of SBS when transmitting 1.5-µm laser in standard single-mode optical fibers under conditions where both time modulation and multi-wavelength operation are employed. Instead of using a conventional continuous-wave (CW), single-wavelength seed laser for the Master Oscillator Power Amplifier (MOPA) system, we introduce a novel configuration in which multiple seed lasers at slightly different wavelengths are employed. These seeders are modulated synchronously at high repetition rates (~10 MHz, with ~50 ns optical pulses) in a complementary manner such that only one laser is active at any given time.
This strategy creates a pseudo-continuous-wave (pseudo-CW) optical field with discrete but relatively narrow spectral components and short temporal pulses. The modulation scheme ensures that the SBS gain medium does not experience a constant optical intensity at any single frequency, thereby disrupting the buildup of the acoustic wave necessary for efficient Brillouin scattering. This complementary modulation technique reduces the effective SBS gain and increases the SBS threshold, allowing significantly higher optical power to be transmitted through the fiber.
This work contributes to the development of SBS-free fiber laser systems capable of delivering high optical powers while retaining narrow linewidths, and it opens new possibilities for applications where stable, high-brightness laser sources are required.
Name: Yair Elmakias
Supervisor: Prof. Mor Mordechai Peretz
Degree: MSc
Subject: Development and IC implementation of Sub-picosecond pulse width modulation (PWM) for power converter control by Yair Elmakias
