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Sweep Stability Characterization of a Vernier-Tuned Distributed Bragg Reflector (VT-DBR) All-Semiconductor Tunable Swept Laser System at 1550 NM for Sensing ApplicationsMartens Biersach, Roric Christian 01 June 2015 (has links) (PDF)
The short-term jitter and longer-term wander of the frequency sweep profile of a Vernier-Tuned Distributed Bragg Reflector (VT-DBR) laser at 1550 nm used in optical coherence tomography (OCT) and other sensing applications is characterized in this work. The VT-DBR has demonstrated success in source-swept OCT (SSOCT), performing both intensity and phase-sensitive OCT.
The purpose of this paper is to investigate one of the unique aspects of the VT-DBR laser that makes it successful in OCT: the stability of the linear optical frequency sweep. A highly stable linear optical frequency sweep implies benefits for further fiber sensing applications including fiber Bragg grating and spectroscopy sensors.
Short-term jitter measurements of the optical frequency sweep are taken using a 3-cavity 100 GHz free spectral range solid etalon, an athermal fiber Bragg grating, a molecular-based gas absorption reference cell, and a Mach-Zehnder interferometer. These four optical filters are used to convert time fluctuations into intensity fluctuations that can be measured by high speed optical receivers. Short term jitter values on the order of 0.5 – 0.6 pm RMS (63 – 82 MHz RMS) are typical values in the VT-DBR lasers systems characterized in this work. This level of jitter is compelling for OCT and fiber-sensing applications.
Longer-term wander is characterized using a multiple-gas absorption reference cell. The long term stability and temperature insensitivity of the absorption cell is ideal for long-term wander characterization of the laser frequency sweeps. Wander values on the order of 2.6 pm of wavelength shift over an 8 hour time frame are reported in this work. The slope of the frequency versus time function of the laser sweep, on the order of 100 MHz/sample, is found to deviate by no more than 0.03% over the same 8 hour time frame. Both the long term wavelength shift and consistency of the slope indicate that these sources will perform well in OCT and fiber sensing applications.
Mechanisms responsible for short-term jitter and longer- term wavelength wander likely include contributions from the laser source itself and from the high speed electronic drive circuitry that creates the wavelength ramp. Investigation of ambient temperature’s influence on the wavelength wander is also highlighted in the work.
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Characterization and Modeling of an O-band 1310 nm Sampled-Grating Distributed Bragg Reflector (SG-DBR) Laser for Optical Coherence Tomography (OCT) ApplicationsTalkington, Desmond Charles 01 June 2013 (has links) (PDF)
In this project, the performance aspects of a new early generation 1310 nm Sampled-Grating Distributed Bragg Reflector (SG-DBR) semiconductor laser are investigated. SG-DBR lasers are ideal for Source Swept Optical Coherence Tomography (SS-OCT), a Fourier-Domain based approach for OCT, necessitating a tunable wavelength source. Three internal sections control the frequency output for tuning, along with two amplifiers for amplitude control. These O-band SG-DBR devices are now being produced in research quantities. SG-DBR lasers have been produced at 1550 and 1600 nm for some times. Fundamental questions regarding the performance of the 1310 nm devices must be quantified. Standard metrics including the laser linewidth, amplitude modulation and frequency modulation responses are characterized. The intrinsic electrical parasitics of the laser diode segments and packaging are also investigated. In addition, testing fixture including a Thermal Electric Cooler (TEC) controller is for the characterization task. Measurements of these key metrics are essential to the enhancement of future devices, aiding in the optimization of more mature products.
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