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Title: Relocking of modes in a detuned fiber AMLL using a balancing sinusoidal input.

November 15, 2018 @ 3:00 pm - 4:00 pm

Date – 15.11.2018

Time – 3.00 p.m.

Venue – ESB 244


Speaker – Shree Krishnamoorthy (EE11D024)


Guides – Dr. Anil Prabhakar and  Dr. Satyajit Mayor (NCBS)


DC Members:

Dr. Harishankar Ramachandran (Chairperson)

Dr. Ananth Krishnan (M)

Dr. Deepa Venkitesh (M)

Dr. Guhan Jayaraman (BT)

Dr. Sujatha.N (AM)




Actively mode-locked fiber ring lasers (AMLLs) are a promising pulsed source for applications in microscopy and spectroscopy that require multiple pulsed lasers in synchronization. In such applications the lasers are used in a master-slave configuration with slave laser driven with a synchronization signal (RF signal at frequency f_i, here) from the master laser. AMLL shows loss of phase-lock in cavity modes when driven by input frequencies f_i away from the AMLL’s resonant frequency (f_0), this is known as detuning which leads to larger pulsewidths and other detrimental effects. To completely tap into AMLLs potential as a slave laser, the issue of detuning needs to be managed. In the last seminar, we discussed the lock-loss in the higher cavity modes of the AMLL due to increasing detuning. We demonstrated that higher modes are susceptible to detuning and the number of modes under phase-lock have a power law relationship to the extent of detuning.


In this talk, we show a novel method to recover a lock-loss of higher modes in the AMLL when subject to detuning. In this method, the cavity of the AMLL is not changed, but an additional sinusoidal signal is provided to recover the lost modes. We show that such an input is capable of recovering the lost locking of higher laser modes by producing cross-coupling terms due to the two  RF inputs for the harmonic modes thereafter. Starting with the mode-locking equations for the cavity modes, we extend the theoretical model for the perturbed AMLL developed in the previous talk to include multiple RF frequencies. Further, using the injection locking framework, the effect on locking state the modes of the AMLL is investigated. We experimentally demonstrate the effect on the modal constituents for two RF input frequencies and access to a larger detuning range of upto 20 kHz made available due to the addition of the second balancing sinusoidal input when compared to the 14 kHz with just a single input for the 10th mode.


Key words—Laser applications, laser modes, laser resonators, lasers, optical fiber lasers, injection locked oscillators, ring lasers, pulsed lasers, synchronization, mode-coupling.


Who will find the talk interesting – Pulsed lasers, laser applications, synchronization between systems like clocks, injection locked systems like PLLs, nonlinear microscopy and spectroscopy using pulsed lasers.


Expected background – an inquisitive mind.


All are cordially invited.


November 15, 2018
3:00 pm - 4:00 pm
Event Category:


ESB – 244
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