All-semiconductor high-speed akinetic swept-source for OCT

Abstract

A novel swept-wavelength laser for optical coherence tomography (OCT) using a monolithic semiconductor device with no moving parts is presented. The laser is a Vernier-Tuned Distributed Bragg Reflector (VT-DBR) structure exhibiting a single longitudinal mode. All-electronic wavelength tuning is achieved at a 200 kHz sweep repetition rate, 20 mW output power, over 100 nm sweep width and coherence length longer than 40 mm. OCT point-spread functions with 45-55 dB dynamic range are demonstrated; lasers at 1550 nm, and now 1310 nm, have been developed. Because the laser's long-term tuning stability allows for electronic sample trigger generation at equal k-space intervals (electronic k-clock), the laser does not need an external optical k-clock for measurement interferometer sampling. The non-resonant, allelectronic tuning allows for continuously adjustable sweep repetition rates from mHz to 100s of kHz. Repetition rate duty cycles are continuously adjustable from single-trigger sweeps to over 99% duty cycle. The source includes a monolithically integrated power leveling feature allowing flat or Gaussian power vs. wavelength profiles. Laser fabrication is based on reliable semiconductor wafer-scale processes, leading to low and rapidly decreasing cost of manufacture.

Diode laser based light sources for biomedical applications

“…Up to several 10 GHz may be acceptable, which results in an OCT imaging depth range of a few millimeters [134,139,140]. In recent years, however, considerable efforts went into the development of swept sources with narrower dynamic linewidth in order to increase the imaging depth range [141][142][143][144].…”

“…Recently, OCT imaging with a VCSEL-based swept source was demonstrated, that supports broadband tuning with sweep rates up to 1 MHz and permits imaging over a depth range larger than 50 mm [157,158]. The other approach is a monolithic diode laser tunable with DBRs in a Vernier-configuration [144]. While these devices require complex control electronics for a broadband sweep without mode-hop artifacts, they offer unprecedented flexibility for adjusting the light source characteristics to various purposes.…”

Sweep Stability Characterization of a Vernier-Tuned Distributed Bragg Reflector (Vt-Dbr) All-Semiconductor Tunable Swept Laser System at 1550 Nm for Sensing Applications

“…Fourier Domain OCT (FDOCT), this method has shown to exhibit a better sensitivity advantage over traditional time domain OCT [3]. The VT-DBR is an ideal source for this approach and has demonstrated success in achieving high resolution images of the human body [4].…”

“…The front mirror (FM), back mirror (BM), and phase (PH) sections of the SG-DBR structure are responsible for wavelength selection [4]. The drive currents of these three frequency-dependent sections induce a change in refractive index of the mirror sections and cause the laser to output a specific wavelength.…”

“…2-10 -It is advantageous in some applications to quickly sweep across two, nonconjoined sweep ranges. The VT-DBR has the ability to output such a noncontiguous laser sweep rapidly, which is impossible with other swept lasers [4]. For example, a sweep of 50 nm at a center wavelength of 1310 nm may take place followed rapidly by another 50 3-2 -An ideal laser sweep is described by its minimum wavelength, λ0 (offset) and optical frequency step (slope), ΔF.…”