Abstract
An optical akinetic swept source (AKSS) at 1060 nm, comprising a 5 m length fiber ring cavity, a semiconductor optical amplifier (SOA) as gain medium, and a 98% reflective chirped fiber Bragg grating as a dispersive element, is described. Active mode-locking was achieved by directly modulating the current of the SOA with sinusoidal signal of frequency equal to 10 times and 20 times the cavity resonance frequency. In the static regime, linewidths as narrow as 60 pm and a tuning bandwidth of 30 nm were achieved, while a 2 mW output power, without any optical booster, was measured dynamically at a sweep speed of 100 kHz. The axial range of the AKSS was evaluated by scanning through the channeled spectrum of a Mach-Zehnder interferometer.
Highlights
Swept source optical coherence tomography (SS-OCT) represents a modern, noninvasive technique of tissue biomedical imaging that uses fast swept narrow linewidth lasers within a sufficiently wide tuning bandwidth [1]
This method requires the use of kilometers of single mode optical fiber (SMF), which makes the total cavity length extremely long, and the application at non-telecom wavelengths is not cost effective
It was demonstrated that by combining two lengths of fiber, one with anomalous dispersion, the dispersion compensating fiber (DCF) and the other with normal dispersion, such as SMF, and the coherence length could be adjusted slightly by the amount of dispersion in the cavity and the mode locking frequency of the signal applied to the semiconductor optical amplifier (SOA) that tunes the gain medium [10]
Summary
Swept source optical coherence tomography (SS-OCT) represents a modern, noninvasive technique of tissue biomedical imaging that uses fast swept narrow linewidth lasers within a sufficiently wide tuning bandwidth [1]. The Fourier domain mode-locking (FDML) method was proposed for a tunable Fabry-Perot based ring laser by extending its delay to values matching its round trip time, and several hundred kHz sweep rates were achieved [5] This method requires the use of kilometers of single mode optical fiber (SMF), which makes the total cavity length extremely long, and the application at non-telecom wavelengths is not cost effective. It was demonstrated that by combining two lengths of fiber, one with anomalous dispersion, the DCF and the other with normal dispersion, such as SMF, and the coherence length could be adjusted slightly by the amount of dispersion in the cavity and the mode locking frequency of the signal applied to the semiconductor optical amplifier (SOA) that tunes the gain medium [10]. A broadband tuning emission and sweeping rates over 100 kHz were achieved
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