Advanced distributed feedback lasers based on composite fiber heavily doped with erbium ions

Abstract

Specially designed composite heavily er 3+-doped fiber in combination with unique point-by-point inscription technology by femtosecond pulses at 1,026 nm enables formation of distributed-feedback (DFB) laser with ultra-short cavity length of 5.3 mm whose parameters are comparable and even better than those for conventional er 3+-doped fiber DFB lasers having much longer cavity. The composite fiber was fabricated by melting rare-earth doped phosphate glass in silica tube. The ultrashort DFB laser generates single-polarization single-frequency radiation at 1,550 nm with narrow linewidth (3.5 kHz) and 0.5 mW output power at 600 mW 980-nm pumping. The same fiber with conventional CW UV (244 nm) inscription technology using phase mask enables fabrication of 40-mm long DFB laser with > 18 mW output power at 3.3% pump conversion, which is a record efficiency for er 3+-doped fiber DFB lasers. The developed technologies form an advanced platform for Er 3+-doped fiber DFB lasers operating around 1.55 µm with excellent output characteristics and unique practical features, in particular, the ultra-short DfB lasers are attractive for sensing applications.

Narrow-Linewidth Er-Doped Fiber Lasers With Random Distributed Feedback Provided By Artificial Rayleigh Scattering

“…As one can see from the lasing spectra in Fig. 4(b-d), the obtained signal-to-noise ratio (SNR) reach 55-60 dB for the lasers based on Fibercore I-25(980/125) and FORC Er 1 wt.% fibers, which 4.5 @ 1550 nm 4.9 @ 1550 nm 5.3-6.3 μm @ 1550 nm Weak signal absorption 1.4 dB/cm @ 980 nm 4 dB/cm @ 1535 nm 0.4 dB/cm @ 980 nm 1.4 dB/cm @ 1535 nm 35-45 dB/m @ 1531 nm Total weak signal absorption for a chosen fiber length 21.7 dB @ 980 nm 62 dB @ 1535 nm 14.8 dB @ 980 nm 51.8 dB @ 1535 nm 43.8-56.8 dB @ 1531 nm Background loss 2 dB/m @ 1300 nm 1 dB/m @ 1300 nm ≤ 10 dB/km @ 1200 nm is comparable with regular DFB lasers [32], and 53 dB for the laser based on FORC Er 3 wt.% fiber.…”

“…3. As an active medium we used commercially available Fibercore I-25(980/125) Er-doped fiber and custom-made heavily-doped fibers (Er 1 wt.% [30], [31] and Er 3 wt.% [32]) fabricated by Fiber Optics Research Center (FORC, Moscow, Russia), whose main parameters are summarized in Table 1. The cavity was pumped by a 980-nm laser diode (LD) with maximal output power of 680 mW.…”

“…Output radiation of a laser co- The use of specialized heavily-doped erbium fibers fabricated by FORC was motivated by the desire to reduce the length of a laser cavity in order to reduce the number of longitudinal modes while maintaining an acceptable level of laser generation efficiency. Since the optical fiber was made by sintering phosphate glass in a silica tube and then drawing the preform [33] an unprecedented level of concentration of erbium ions (1 and 3 wt.%) without their clustering was achieved in the used fiber waveguides [32].…”

Er-doped fiber laser with regular and random distributed feedback

“…Distributed feedback (DFB) fiber lasers are known as a unique source of single-frequency lasing for a wide variety of applications from spectroscopy [1] to precision sensing [2], thanks to the high stability, low noise level (signal to noise ratio > 65 dB), and narrow linewidth (<1 kHz). The cavity of distributed feedback fiber lasers is usually based on a periodic structure such as pi-phase-shifted fiber Bragg grating (FBG) which is embedded into an active fiber, so that a stable single-frequency regime is provided [3]. In contrast, random distributed feedback (RDFB) fiber lasers usually utilize Rayleigh scattering on a natural or artificial random refractive index structures.…”

Волоконные Лазеры С Распределенной Обратной Связью На Основе Регулярных И Случайных Структур Показателя Преломления

“…В частности, технология поточечной фс модификации позволила создать РОС-лазер рекордно короткой длины (5,3 мм) в композитном эрбиевом световоде [5], причем его характеристики не уступают характеристикам обычных волоконных РОС-лазеров с длиной резонатора на порядок больше, в частности, измеренная ширина линии составила единицы кГц при мощности 0,5 мВт. С помощью фс технологии в пассивном волокне длиной 5-10 см был сформирован искусственный рэлеевский отражательон имеет малые потери и в комбинации с эрбиевым РОС-лазером такой гибридный лазер с регулярной и случайной РОС позволяет на порядок уменьшить ширину линии одночастотной генерации (с ~1 до ~0,1 кГц) в телекоммуникационном диапазоне спектра (~1,55 мкм).…”