Stable Narrow Linewidth Research Articles

Single-frequency erbium-doped fiber laser based on self-injection feedback

In this paper, a single-frequency erbium-doped fiber laser based on self-injection feedback is reported, which uses a high-reflectivity broadband fiber Bragg grating, an ordinary commercial high-doped erbium fiber and a low-reflectivity broadband fiber Bragg grating to form the main resonant cavity, and a stable narrow linewidth single-frequency laser output is achieved by connecting a single-mode fiber and a low reflectivity narrowband fiber Bragg grating to form self-injection feedback. Then, a saturated double-pass erbium-doped fiber amplifier and a saturable absorber were added to the self-injection optical path, which well suppressed the relative intensity noise and phase noise and the relaxation oscillation intensity was well suppressed by about 18.08 dB, and the phase noise was 36.7dBc·Hz−1 suppression, the edge-mode rejection ratio is increased by 13 dB, and the final laser linewidth is about 270 Hz, and the output power is 8.5 dBm.

Broadband fiber laser with selective and stable narrow linewidth wavelength over 68 nm selectable bandwidth

Broadband fiber laser with selective and stable narrow linewidth wavelength over 68 nm selectable bandwidth

Stable tunable narrow-linewidth fiber laser based on random distributed feedback

Stable narrow linewidth fiber lasers with relatively high output power have broad application prospects in optical communication, sensing and precision measurement, due to their high coherence and low noise characteristics, which are the main requirements to increase the detection range and accuracy of these systems. Obtaining narrow linewidth laser output with improved performance has been one key topic in the field of laser science and technology. Here, we propose a combination of transmission and reflection of randomly distributed Bragg grating arrays to compress the linewidth of laser emission in an Erbium-doped fiber system at the 1550 nm band, thereby providing a selective reflection-transmission channel effect without too many feedback points. A stable narrow linewidth fiber laser with a linewidth of 570 Hz (output power of 6 mW) and 830 Hz (output power amplified to 25 mW), a maximum signal-to-noise ratio (SNR) greater than 63 dB, and a wavelength adjustable in the range of 445 pm is realized.

Dynamics of Semiconductor Lasers under External Optical Feedback from Both Sides of the Laser Cavity

To increase the spectral efficiency of coherent communication systems, lasers with ever-narrower linewidths are required as they enable higher-order modulation formats with lower bit-error rates. In particular, semiconductor lasers are a key component due to their compactness, low power consumption, and potential for mass production. In field-testing scenarios their output is coupled to a fiber, making them susceptible to external optical feedback (EOF). This has a detrimental effect on its stability, thus it is traditionally countered by employing, for example, optical isolators and angled output waveguides. In this work, EOF is explored in a novel way with the aim to reduce and stabilize the laser linewidth. EOF has been traditionally studied in the case where it is applied to only one side of the laser cavity. In contrast, this work gives a generalization to the case of feedback on both sides. It is implemented using photonic components available via generic foundry platforms, thus creating a path towards devices with high technology-readiness level. Numerical results shows an improvement in performance of the double-feedback case with respect to the single-feedback case. In particularly, by appropriately selecting the phase of the feedback from both sides, a broad stability regime is discovered. This work paves the way towards low-cost, integrated and stable narrow-linewidth integrated lasers.

Modulation bandwidth enhanced self-injection locking laser with an external high-Q microring reflector.

We propose and demonstrate a hybrid modulation bandwidth enhanced self-injection locking laser by butt coupling a commercial distributed feedback laser with an external high-Q silicon nitride microring reflector (MRR). The MRR keeps the laser in strong self-injection locking state with photon-photon resonance, which can realize direct modulation bandwidth enhanced and stable narrow linewidth single-mode output. With the further optimization of MRR parameters, the 3-dB modulation bandwidth and the linewidth of the hybrid laser are enhanced to 15.28 GHz from 7.70 GHz and narrowed to 4 kHz from 600 kHz, respectively. This work makes full use of the advantages of self-injection and integrated photonic technology, which has potential applications in many fields.

All-fiber single-longitudinal-mode narrow linewidth fiber ring laser with cylindrical vector beam output

A single-longitudinal-mode (SLM) fiber ring laser with cylindrical vector beam (CVB) output is experimentally demonstrated. Mode selection and spectrum filtering are achieved by introducing a two-mode fiber Bragg grating (TM-FBG) as an output mirror simultaneously. The SLM operation is obtained by using a compound ring cavity laser structure together with an un-pumped EDF acting as a saturable absorber. The fiber laser operates at a single wavelength of 1545.99 nm with a 20 dB linewidth of about 7.1 kHz and an optical signal to noise ratio of more than 68 dB. Through adjusting the intra-cavity polarization controllers, stable narrow linewidth radially and azimuthally polarized CVBs are both obtained.

Study of fiber laser micro-nano sensor based on colloidal crystal

A fiber laser micro-nano sensor based on colloidal crystal structure is proposed in this paper. The fiber laser has stable frequency and narrow linewidth. It is realized by using an unpumped erbium-doped fiber (EDF) as the saturable absorber. The saturable absorber possesses the shape of taper. The laser threshold can be effectively reduced by the tapered saturable absorber. The tapered fiber coated with colloidal crystal as sensing unit is studied. The concentration of ethanol can be obtained from the detection of the output laser wavelength. It can be extensively used in chemical, medical and biological detections.

A Stable and Switchable Narrow Linewidth Fiber Laser

A switchable fiber laser based on Mach-Zehnder interferometer (MZI) and photonic crystal fiber (PCF) is demonstrated. A section of PCF in the fiber laser is used to induce four-wave mixings (FWM) effect and MZI acts as a comb filter. Experimental results show that stable single-wavelength, dual-wavelength and triple-wavelength operations can be obtained with the adjustment of the polarization controller. The power of two peaks of the dual-wavelength laser is almost the same under room temperature with an output power fluctuation less than 0.6dB. The advantages of the proposed fiber laser include quite stable wavelength and narrow linewidth owing to the contributions of FWM in the PCF.

Stable Narrow Linewidth 689 nm Diode Laser for the Second Stage Cooling and Trapping of Strontium Atoms

We report stable narrow linewidth laser systems based on self-developed Littman configuration external cavity diode lasers (ECDLs). The frequency of the ECDL is stabilized to a high fineness ultralow-expansion glass reference cavity with the Pound-Drever-Hall technique. By heterodyne beating of two identical systems, we conclude that the linewidth of each ECDL is reduced to lower than 150 Hz and its frequency stability reaches 4.3 × 10-14 at an averaging time of 1s, the averaged long-term frequency drift is less than 0.2 Hz/s over 30 h measurement time.

Highly efficient temporally stable narrow linewidth cryogenically cooled Yb-fiber laser

Cryogenic cooling is an effective way of increasing the efficiency in many solid-state lasers. In fiber lasers however, while the efficiency is increased, a reduced reabsorption in combination with reduced homogeneous broadening tends to broaden the linewidth, yielding a low spectral power density of the laser emission. In this work we lock a cryogenically-cooled Yb-doped fiber laser with a volume Bragg grating to overcome this problem and achieve a temporally stable narrow linewidth highly efficient laser. We extract 11.4-W of output power in spectral window of less than 0.4-nm with 14.5-W of launched pump light.

Stable narrow linewidth Er‐doped fiber laser at 1550 nm

AbstractA narrow linewidth fiber laser based on fiber Bragg grating Fabry‐Perot etalon is demonstrated. Spatial hole burning effect is restrained by fiber Faraday rotator. The short fiber Bragg grating Fabry‐Perot etalon as narrow bandwidth filter discriminates and selects laser longitudinal modes efficiently. Stable single frequency 1550 nm laser is acquired. Pumped by 976 nm laser diode, the fiber laser exhibits 11 mW threshold. Output power (50 mW) is obtained upon the 200 mW pump power. Optical‐optical efficiency is 25% and slope efficiency is 27%. The linewidth of laser is less than 10 kHz, measured by the delayed self‐heterodyne method with 10 km single mode fiber. In addition, the lasing linewidth keeps less than 10 kHz over 1 nm tuning range in the temperature tuning experiment. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1453–1456, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22439

Frequency modulated and polarization maintaining fiber laser with narrow linewidth

A novel configuration of fiber laser with frequency modulation is presented. Frequency modulation, stable polarization state and narrow linewidth are realized by using the waveguide phase modulator, polarization maintaining devices and saturable absorber. It is shown that the laser output reaches 23 mW, linewidth is less than 1 kHz, polarization extinction ratio is higher than 20 dB and maximum value of frequency deviation can reach 7.5 MHz.

Realization of Stable Narrow Linewidth Dual-Wavelength Lasingin an Erbium-Doped Fibre Laser by Cleaving the Wavelength-SelectiveFilter Spectrum

We propose and demonstrate a new concept of stable narrow-line-width andclose wavelength spacing dual-wavelength lasing in an Er-doped fibrering laser (EDFRL) by cleaving the spectrum with a wavelength-selectivecomponent in the EDFRL. A fibre loop mirror (FLM) combining with apolarization controller (PC) acts as the cleaver. The cleaver canproduce a fine pectinate spectrum. By adjusting the PC, the finepectinate spectrum can be so changeable that cleaving the spectrum of afibre Bragg grating (FBG) into two parts. As a result, we obtain thedual-wavelength fibre lasering with a bandwidth of only 0.03 nm anda wavelength spacing of only 0.07 nm. Furthermore, the laser can alsoperform stable switchable single wavelength or stabledifferent-bandwidth dual-wavelength by carefully adjusting the PC atroom temperature.

Yb3+doped double-clad fiber laser based on fiber Bragg grating

Fiber Bragg grating (FBG) was successfully fabricated in a Yb3+ doped double clad fiber with D-shaped inner-cladding by using phase mask method. Based on the FBG, a stable narrow line width double clad fiber laser was successfully demonstrated which resolved the output instability caused by mode-competition in common double-clad fiber lasers. The maximum output power is 570?mW at the wavelength 1058.2nm with 0.196nm line-band. Based on rate equations, the relationship between output power and pump power, the reflectivity of the FBG and the optimized length of the fiber were analyzed, which were in good agreement with the experimental results.

Narrow linewidth tunable operation of Er3+-doped single-mode fibre laser

Wavelength tunable operation of an Er3+-doped fibre laser has been demonstrated using a tunable ring resonator configuration. This configuration gives a stable narrow linewidth output exhibiting discrete tuning bands within a 70 nm wavelength region centred on the important 1550 nm telecommunications window.

Oscillation frequency tuning characteristics of fiber-extended-cavity distributed-feedback lasers

Stable narrow-linewidth (<100 kHz) operation has been demonstrated for a fiber-extended-cavity distributed-feedback (EC DFB) laser emitting at 1.55 μm wavelength. We describe the observed oscillation frequency tuning characteristics of the laser obtained by controlling the temperature and injection current. The effects of distributed grating reflection and continuous frequency tuning schemes are examined for both the EC DFB laser and for the case of an EC DBR (distributed Bragg reflector) laser.

Spectral linewidth of an AlGaAs/GaAs DFB-TJS external-cavity laser with optical phase control loop

A stable narrow spectral linewidth was obtained for an external-cavity laser consisting of an AlGaAs/GaAs distributed-feedback laper and a stabilised electro-optical feedback loop. The linewidth of 500kHz with its fluctuation of less than ±5 kHz was achieved without any temperature control.