Unlocking Clearer Images: Enhancing Laser Precision and Reducing Noise in FDMLLasers for Medical Imaging

Industry: The research focuses on the optics and photonics industry, specifically in the
development and optimization of laser technologies for applications such as optical coherence
tomography (OCT) in medical imaging.

Challenge: The main challenge addressed in this study is the impact of chromatic dispersion
on the coherence length and noise of Fourier Domain Mode Locked (FDML) lasers. These
factors are critical for ensuring high-quality imaging and accurate measurements in applications
like OCT.

Extraordinary Aspects of the Paper: The paper demonstrates a significant reduction in
laser linewidth, achieving an instantaneous linewidth of 20 pm. It also highlights the laser’s
exceptional relative intensity noise (RIN) performance, achieving -136 dBc/Hz. Additionally, the
study introduces a robust method to measure coherence and noise properties, which can be
beneficial for optimizing FDML lasers for various applications.

Equipment & Sensors Used:

GaGe Digitizer: Model CS12400, 14-bit ADC, 200 MS/s sampling rate (GaGe Applied
Technologies).

Ultrasonic Transducer: Central frequency of 35 MHz (NIH Ultrasonic Transducer Resource
Center, USC, CA).

Semiconductor Optical Amplifier (SOA): Type BOA1004 (Covega Corp.), polarization-
dependent broadband gain medium centered at 1550 nm.

Photo Receiver: 100 MHz bandwidth (Thorlabs, type PDB150C) with a 100 MHz low-pass filter
(Mini-Circuits).

Mach Zehnder Interferometer (MZI): Includes a variable delay line actuated by a step motor,
controlled by a PC.

Photo Diode: 1 GHz bandwidth (Menlo Systems, model FPD310).

Digital Oscilloscope:: 2.5 GS/s with 8-bit resolution (Tektronix, model DPO7104).

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