Abstract
A prism-based self-injection locked seamlessly tunable blue InGaN/GaN laser diode composite cavity system is presented. A rigorous analysis of this external cavity diode laser (ECDL) system is performed at two different optical feedback powers. At 130 mA low injection, the high reflection system (HRS) exhibits a record wideband tuning span of ∼12.11 nm with a side-mode-suppression-ratio (SMSR) ≥ 15 dB, measuring as high as 40 dB, linewidth ≤110 pm, and a working power of about 3 mW. Whereas, a tuning range of 8 nm with linewidth ≤88 pm, SMSR ≥ 13 dB, reaching a maximum of 35 dB with 14.5 mW usable power is achieved from the low reflection system (LRS) at the same injection current. Moreover, an inverse relationship between the optical power and the tunability is observed in both the systems with a value as high as 180 mW exhibited by LRS configuration and attaining a tunability of 4.5 nm. Both systems highlight high stability even at higher injection currents and temperature. Such a robust, simple, and compact system may serve as a crucial light source in a plethora of diverse applications besides visible optical communications. To the best of our knowledge, this is the first report on a continuously tunable self-injection locked tunable laser system.
Highlights
Tunable and narrow linewidth semiconductor laser diode systems in blue-violet region are indispensable sources in many applications; ranging from trace matter detection [1], biophotonics and bio-imaging [2], high resolution atomic and molecular spectroscopy [3], [4], holographic display and data storage [5], laser cooling [6], gas trace measurement [7], to sources for frequency conversion [8], and so on
The 8% usable optical power of the system is coupled into an optical fiber via a plano-convex lens (Thorlabs, LA-1951-A) L1 while the other fiber end is connected to an optical spectrum analyzer (Yokogawa, AQ6373B, 20 pm resolution) via a fiber connector (FC) for diagnostic purpose
L-I-V characteristics of the FR ∼450 nm blue Fabry Perot (FP) laser diode are measured at room temperature (20 °C) and are shown in Fig. 2(a) wherein a threshold current (Ith) of about 124 mA is apparent
Summary
Tunable and narrow linewidth semiconductor laser diode systems in blue-violet region are indispensable sources in many applications; ranging from trace matter detection [1], biophotonics and bio-imaging [2], high resolution atomic and molecular spectroscopy [3], [4], holographic display and data storage [5], laser cooling [6], gas trace measurement [7], to sources for frequency conversion [8], and so on Inherent features, such as simplicity, small footprint, cost-effective, and longer lifetime and efficiency, compared to their counterparts, for instance, metal-vapor, dye, Vol 12, No 2, April 2020. Monolithic integration of DFB gratings, as well as multi-section device fabrication on GaN, is still in the initial stage due to its sophisticated fabrication techniques and complexity, adding to increased device cost
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