Wavelength Selective Element Research Articles

Wide wavelength selectable all-fiber thulium doped fiber laser between 1925 nm and 2200 nm

We demonstrate an all-fiber Tm(3+)-doped silica fiber laser operating at a wide selectable wavelength range by using different fiber Bragg gratings (FBGs) as wavelength selection elements. With a specifically designed high reflective (HR) FBG and the fiber end as an output coupler, the lasing in the range from 1975 nm to 2150 nm with slope efficiency of >30% can be achieved. By employing a low reflective (LR) FBG as the output coupler, the obtainable wavelengths were extended to the range between 1925 nm and 2200 nm which is the reported longest wavelength from the Tm(3+)-doped silica fiber lasers. Furthermore, by employing a FBG array in the laser cavity and inducing bend loss between adjacent FBGs in the array, six switchable lasing wavelengths were achieved.

A switchable dual-wavelength erbium-doped fiber laser based on Sagnac loop inserted with two FBGs

A novel switchable dual-wavelength erbium-doped fiber (EDF) laser is demonstrated. The wavelength selection element consists of two fiber Bragg gratings (FBGs), a polarization controller (PC) and a 3 dB coupler forming a Sagnac loop inserted with two FBGs. We study the effect of coupling ratio on filtering performance in this paper. By adjusting PC, we can change the wavelength-dependent loss, and then using nonlinear polarization rotation effect to suppress the mode competition caused by the homogeneous broadening of EDF, we obtain single- and double-wavelength laser outputs. At room temperature, under 200 mW pump power, dual-wavelength laser is achieved, and the center wavelengths are 1545.34 nm and 1548.20 nm, respectively. The peak power values are −13.36 dBm and −14.58 dBm, and side mode suppression ratios (SMSRs) are 41.10 dB and 39.88 dB, respectively. Within two hours, the maximum fluctuation of peak power is less than 0.7 dB, which shows that the demonstrated fiber laser is stable. Moreover, by adjusting PC, singel-wavelength laser output is obtained, the peak power is −6.27 dBm or −5.45 dBm, and SMSR is 40.03 dB or 39.96 dB at 1545.34 nm or 1548.20 nm, respectively.

Simultaneous dual-wavelength operation around 1.06 μm of a LD-end-pumped, passively Q-switched Nd:GGG laser with GaAs as saturable absorber

By using neodymium-doped gadolinium gallium garnet (Nd:GGG) as the laser medium, a passively Q-switched simultaneous dual-wavelength Nd:GGG laser with a GaAs saturable absorber has been realized. The Nd:GGG laser operates at a stable dual-wavelength peaked at 1060.8 and 1062.7 nm without any wavelength selective elements in the cavity. Stable Q-switched pulses with a shortest duration of 6 ns have been obtained, corresponding to a single pulse energy of 2.1 μJ and a peak power of 335 W.

Multiwavelength narrow linewidth erbium-doped fiber laser based on FP-LDs

In this paper, we propose and demonstrate a technique to realize multiwavelength operation in erbium-doped fiber lasers (EDFLs) by inserting two Fabry Pérot laser diodes (FP-LDs) in the laser cavity respectively in cascaded and parallel way. The FP-LDs not only act as wavelength selection elements, but also offer optical gain or loss for the operation wavelengths in the laser cavity. The gains or losses for the oscillation wavelengths obtained from FP-LDs differ with adjustment of the driving current of the FP-LDs. Thus, the utilization of the FP-LDs in the laser cavity can introduce wavelength dependent gain or loss which can effectively suppress the competition caused by the homogeneous gain broadening of the erbium-doped fiber (EDF). As a result, 16-wavelength and 20-wavelength operation with a wavelength-spacing of 1.25 nm has been achieved respectively in the cascaded and parallel FP-LDs based EDFL schemes. The measured power fluctuation of each wavelength is smaller than 0.4dB for both EDFLs. Furthermore, the injection locking of the FP-LDs ensures a narrow linewidth of the EDFL output and the linewidth is estimated to be narrower than 100 MHz for the cascaded scheme based EDFL.

Stable and wavelength-tunable silicon-micro-ring-resonator based erbium-doped fiber laser

In this work, we propose and demonstrate a stable and wavelength-tunable erbium-doped fiber (EDF) ring laser. Here, a silicon-on-insulator (SOI)-based silicon-micro-ring-resonator (SMRR) is used as the wavelength selective element inside the fiber ring cavity. A uniform period grating coupler (GC) is used to couple between the SMRR and single mode fiber (SMF) and serves also as a polarization dependent element in the cavity. The output lasing wavelength of the proposed fiber laser can be tuned at a tuning step of 2 nm (defined by the free spectral range (FSR) of the SMRR) in a bandwidth of 35.2 nm (1532.00 to 1567.20 nm), which is defined by the gain of the EDF. The optical-signal-to-noise-ratio (OSNR) of each lasing wavelength is larger than 42.0 dB. In addition, the output stabilities of power and wavelength are also discussed.

Guided-Mode Resonance Filters for Wavelength Selection in Mid-Infrared Fiber Lasers

A narrowband mid-infrared (mid-IR) guided-mode resonance filter (GMRF) is designed and fabricated using a Hafnium Dioxide film/quartz wafer material system. The fabricated GMRF is then integrated into an erbium (Er)-doped Zr-Ba-La-Al-Na (ZBLAN) fluoride glass fiber laser as a wavelength selective feedback element. The laser operated at 2782 nm with a line-width less than 2 nm demonstrates the viability of GMRFs for wavelength selection in the mid-IR.

Characterization of Transient Response in Fiber Grating Fabry–Perot Lasers

A comprehensive study on the transient response of fiber-grating Fabry-Perot (FGFP) laser is numerically conducted. Fiber Bragg grating (FBG) is used as a wavelength selective element to control the external optical feedback (OFB) level. In addition to the external OFB level, the effect of other external cavity parameters such as temperature, injection current, dc-bias level, coupling coefficient, and gain compression factor on transient response characteristics of the laser are investigated. The temperature dependence (TD) of response characteristics is calculated according to TD of laser parameters instead of well-known Pankove relationship. Results show that, by increasing the laser injection current, the relaxation oscillation's amplitude, frequency, and damping rate are increased, while the laser turn-on time delay is reduced. In addition to the injection current and dc-bias level, the turn-on time delay can be reduced by increasing OFB reflectivity. It is shown that the optimum external fiber length (Lext) is 3.1 cm and the optimum range of working temperature for FGFP laser is within ±2°C from the FBG reference temperature (To). Also, it is shown that antireflection (AR) coating facet reflectivity value of 1 ×10-2 is sufficient for the laser to operate at good response characteristics with low fabrication complexity.

Low‐resolution Raman spectroscopy over a wide spectral range with a single‐diffraction order arrayed‐waveguide grating

An integrated arrayed‐waveguide grating (AWG) fabricated in silicon oxynitride (SiON) technology is used as the wavelength separation and selection element for Raman spectroscopy. With a spectral resolution of 5.5 nm and a free spectral range of 215 nm, the AWG enables wavelength separation of the full Raman fingerprint region in a single diffraction order without order overlap. It is demonstrated that Raman signal detection of cyclohexane with the AWG is feasible and that the information on position and relative intensities of the Raman bands of cyclohexane are preserved. A detailed description of the signal processing methodology to obtain AWG‐based Raman measurements corrected for instrument response is presented. The Raman measurement based on the integrated intensity output of the device corresponds well to the expected relative intensity channel output of the AWG. Raman information based on band intensity ratios from the AWG channels is also preserved compared with the spectral integration of bands, with a maximum relative error of 9% attributed to some light that might have leaked from the channels to the device substrate. These results are a step towards the realization of a technology suitable for dedicated, low‐cost, miniaturized Raman devices. Copyright © 2012 John Wiley & Sons, Ltd.

Silicon photonic MZI sensor array employing on-chip wavelength multiplexing

In this work, we present a novel wavelength multiplexing concept for an integrated label-free biosensor array employing silicon photonic Mach-Zehnder interferometers as sensors. Microring resonators act as wavelength selective elements in order to address the individual interferometers. Wire Bragg gratings terminate the interferometer arms and reflect the light back, which eliminates the risk of a wavelength mismatch between drop and add port. The characteristics of the device are discussed and the design based on FEM and 3D-FDTD simulations as well as measurements of the nanophotonic key components—micro ring resonators, Mach-Zehnder interferometers and photonic wire Bragg gratings—are presented. Measurements of combinations of the wire Bragg gratings with ring resonators and Mach-Zehnder interferometer sensors demonstrate the applicability of the reflectors in photonic circuits.

Experimental observation of lasering behavior in wavelength-switchable fiber laser with arrayed waveguide grating

A simple and wavelength-switchable fiber laser consisting mainly of an Erbium-doped fiber amplifier (EDFA) which provides the optical gain and an 1×40 (1 input channel to 40 output channels) arrayed waveguide grating (AWG) that supports wavelength selection is reported. The lasering behavior in wavelength-switchable fiber laser is investigated experimentally. One can obtain wavelength-switchable single-longitudinal-mode (SLM) single wavelength laser with different wavelength by changing different channel of the AWG as the wavelength selection element. Lasering wavelength hopping in dual wavelength laser operation for low pump power is experimentally observed. The wavelength hopping and the output power of the laser is controlled by using a variable optical attenuator (VOA). The wavelength hopping operation is eliminated for high pump power. One can obtain switchable dual wavelength laser with different wavelength by selecting different two channels of the AWG. The output laser exhibits a good performance having a high sidemode suppression ratio (SMSR), narrow line-width and symmetrical spectrum.

Experimental Method to Find the Optimum Excitation Waveform to Quench Mechanical Resonances of Fabry–Pérot Tunable Filters Used in Swept Sources

We report experimental evidence of improving the nonlinearity of conventional wavelength swept laser sources based on a fiber Fabry-Perot tunable filter as a wavelength-selective element. Our solution is based on applying a nonsinusoidal, synthesized waveform to the tunable filter that can be identified experimentally. A significant improvement in the optical coherence tomography image quality has been obtained without any software recalibration method.

Ultra-Widely Tunable, Narrow Linewidth Picosecond Fiber-Optical Parametric Oscillator

We demonstrate a picosecond fiber-optical parametric oscillator with an ultrawide tuning range pumped by a relatively low-cost intensity-modulated pump. The tuning range of the oscillator is from 1320 to 1520 nm and from 1580 to 1820 nm, which is as wide as 440 nm, with a wavelength span of 500 nm. A 40-m dispersion-shifted fiber is employed inside a cavity as the parametric gain medium. In the wavelength region from 1320 to 1395 nm and from 1720 to 1820 nm, the linewidth of the sideband is less than 1 nm without the use of any wavelength-selective element inside the cavity. Pulses with pulsewidths from 7 to 17 ps are generated.

Fast and wide tuning wavelength-swept source based on dispersion-tuned fiber optical parametric oscillator

We demonstrate a dispersion-tuned fiber optical parametric oscillator (FOPO)-based swept source with a sweep rate of 40 kHz and a wavelength tuning range of 109 nm around 1550 nm. The cumulative speed exceeds 4,000,000 nm/s. The FOPO is pumped by a sinusoidally modulated pump, which is driven by a clock sweeping linearly from 1 to 1.0006 GHz. A spool of dispersion-compensating fiber is added inside the cavity to perform dispersion tuning. The instantaneous linewidth is 0.8 nm without the use of any wavelength selective element inside the cavity. 1 GHz pulses with pulse width of 150 ps are generated.

Tunable and reconfigurable multiwavelength fiber optical parametric oscillator with 25 GHz spacing

We demonstrate a multiwavelength fiber optical parametric oscillator based on a nonlinear fiber as the gain medium. Using a transmission grating filter cascaded with a programmable filter as wavelength-selective elements, we achieve multiwavelength operation with 129 lasing wavelengths spaced apart by 25GHz. The power nonuniformity is less than 4.5dB with a power fluctuation of less than 0.1dB over a 20min period. Moreover, we realize tunable and reconfigurable functions over the entire lasing spectrum (approximately 25.6 nm), which greatly enhances the performance and flexibility of this laser.

10.1007/s11490-008-3027-1

We report on a wide wavelength tuning in a double-clad ytterbium-doped fiber laser. The laser cavity consists of an array of broadband high-reflection fiber Bragg gratings and a bulk grating as the output coupler and wavelength selection element. The proposed fiber laser configuration combines a low intracavity loss of the fiber Bragg grating mirrors with a wide wavelength tuning of the bulk gratings. We demonstrate a >70-nm wavelength tuning range, limited only by the available fiber Bragg gratings.

Wavelength Tunable Laser Using an Interleaved Rear Reflector

A novel integrated reflector concept for use in widely tunable semiconductor lasers is introduced. Two concatenated Fabry-Perot cavities with low partial reflections and different cavity lengths are interleaved to realize a wavelength-selective reflective element. Differential current injection in the interleaved cavities is used to tune the reflection peak. The reflector is integrated in an all-active multisection device. The laser tunes across 37 wavelength channels on a 100-GHz grid over a wavelength span of 30 nm. The linewidth of each mode is <7 MHz while the power deviation is <6 dB.

A NEW APPROACH TO DESIGN DIGITALLY TUNABLE OPTICAL FILTER SYSTEM FOR DWDM OPTICAL NETWORKS

A new approach to design digitally tunable optical fllter system for DWDM (Dense Wavelength Division Multiplexed) optical networks is presented. This digitally tunable optical fllter system uses semiconductor optical ampliflers (SOAs) and DWDM thin fllm fllter based wavelength selection elements. The design is very easy to conflgure, expand and reduce. This digitally tunable optical fllter system is smaller in size, lesser in weight, cheaper in cost, consumes low power and has better timing performance as compared to digitally tunable optical fllter suggested by researchers recently.

Time-resolved characterization of external-cavity quantum-cascade lasers

We report on the temporal and spectral evolution of the lasing spectrum of an external-cavity quantum-cascade (QC) laser operated in pulsed mode. Time-resolved lasing spectra, recorded on nanosecond time scale, revealed that after turn-on of the 100 ns current pulse multiple-mode lasing starts at the gain maximum of the QC laser controlled by the cavity formed by the chip facets. Depending on the spectral tuning after a time delay of 15–35 ns, the QC laser couples to the external cavity as seen from a change in lasing wavelength to that defined by the external grating as wavelength selective element.

基于啁啾莫尔光栅和半导体光放大器的多波长光纤激光器

A simple and cost-effective multi-wavelength fiber ring laser based on a chirped Moire fiber grating (CMFG) and a semiconductor optical amplifier (SOA) is proposed. Stable triple-wavelength lasing oscillations at room temperature are experimentally demonstrated. The measured optical signal-to-noise ratio (SNR) reaches the highest value of 50 dB and the power fluctuation of each wavelength is less than 0.2 dB within a 1-h period. To serve as a wavelength selective element, the CMFG possesses excellent comb-like filtering characteristics including stable wavelength interval and ultra-narrow passband, and its fabrication method is easy and flexible. The lasing oscillation shows a narrower bandwidth than SOA-based multi-wavelength fiber lasers utilizing some other kinds of wavelength selective components. Methods to optimize the laser performance are also discussed.

NEW APPROACH TO DESIGN DIGITALLY TUNABLE OPTICAL FILTER SYSTEM FOR WAVELENGTH SELECTIVE SWITCHING BASED OPTICAL NETWORKS

A new approach to design digitally tunable optical fllter system by using semiconductor optical ampliflers (SOAs) and Dense Wavelength Division Multiplexed (D.W.D.M.) thin fllm fllter based wavelength selection elements is presented. The system designed with this approach is very easy to conflgure and expand, smaller in size, lesser in weight, cheaper in cost and consuming less power as compared to design suggested by other researchers recently.