Number Of Laser Lines Research Articles

Sagnac-interferometer-based multiwavelength SOA fiber laser assisted by an intensity-dependent loss mechanism.

We demonstrate a Sagnac-interferometer-based multiwavelength fiber laser with an intensity-dependent loss (IDL) mechanism in the L-band region using a semiconductor optical amplifier (SOA) as the gain medium. The IDL mechanism flattens and stabilizes the multiwavelength spectrum. We also investigate the effect of rotation angles of polarization controllers (PCs) at different polarization devices on multiwavelength performance. At best settings, 31 lasing lines within 3dB uniformity were generated with an extinction ratio (ER) of 17dB. Adjusting the half-wave plate of PC1 and PC2 from 0° to 90° shifted the multiwavelength output by 0.01nm and 0.072nm, respectively. PC2 adjustment also affects the multiwavelength flatness as compared to PC1. Furthermore, the number of lasing lines and the ER were directly influenced by the SOA current.

Nonlinearity Effect on Multiwavelength fiber laser based on Sagnac loop mirror interferometer

This paper demonstrates a multiwavelength fiber laser (MWFL) with erbiumdoped fiber amplifier (EDFA) as gain medium and Sagnac loop mirror interferometer as filter. Stable and flat lasing spectrum was achieved when highly nonlinear fiber (HNLF) was inserted into the laser cavity. The number of lasing lines and extinction ratio (ER) was directly influenced by EDFA gain where at maximum setting, 14 lasing lines with ER of 19 dB were generated. The stable and flat spectrum achieved spanned about 1.6 nm. This is due to the induced intensity dependent loss mechanism in the cavity by adjusting the half-wave plate of the polarization controller in combination with the HNLF. The MWFL output showed peak power variation of about 2.1 dB within 100 minutes of observation time.

Effect of polarization adjustment towards the performance of SOA-based multiwavelength fiber laser

We investigate the performance of multiwavelength fiber laser (MWFL) at six simultaneous angle settings of half wave plate (HWP) and quarter wave plate (QWP) using two different types of semiconductor optical amplifiers (SOAs): a booster amplifier and an in-line amplifier. In order to generate multiwavelength, a Lyot filter is inserted into the cavity to serve as a comb filter. MWFL using the booster optical amplifier (BOA) shows superior performance in terms of spectrum range, number of lasing lines, and extinction ratio (ER). The laser stability is excellent where all the output peaks experience a minor power fluctuation with maximum value of 0.28 dB within 100 min of observation time.

Multi-Wavelength SOA Fiber Laser With Ultra-Narrow Wavelength Spacing Based on NPR Effect

A multi-wavelength semiconductor optical amplifier (SOA) fiber laser with ultra-narrow wavelength spacing is experimentally demonstrated in this paper. The SOA is used as the primary gain medium due to its inhomogeneous broadening and nonlinear polarization rotation (NPR) effect that allows to achieve stable multi-wavelength output with ultra-narrow wavelength spacing. The combination of PC (polarization controller)-SOA-PC-polarizer and nonlinear optical loop mirror (NOLM) serve as the intensity equalizer for inducing IDL to suppress mode competition effect furtherly, while the NOLM mainly achieves power equalization and improve SMSR in this laser. The Lyot-Sagnac loop mirror is designed to realize different channel spacing, when the length of PMF is 71 m, stable multi-wavelength output has been achieved at room temperature. The number of lasing lines is up to 184 with wavelength spacing of 0.08 nm within 10 dB bandwidth from 1549.75 nm to 1664.25 nm, and all peaks experience some minor power fluctuation, and the maximum value is about 5 dB. The side mode suppression ratio (SMSR) is about up to 22 dB. Moreover, the maximum value of optical signal-to-noise ratios (OSNR) is 10.7 dB.

Stable multiwavelength semiconductor amplifier fiber laser based on nonlinear fiber loop mirror

A stable multiwavelength semiconductor amplifier (SOA) fiber laser using a nonlinear fiber loop mirror (NOLM) and a Lyot–Sagnac loop mirror is presented and experimentally demonstrated. The Lyot–Sagnac loop mirror serves as a wavelength selection device, and the wavelength spacing is controlled by the length of polarization-maintained fiber (PMF). The NOLM serves as a power equalizer to achieve power equalization and improve stability. Moreover, the NOLM can also suppress the mode competition effect within homogenous broadening linewidth of SOA. Multiwavelength output with power equality has been achieved at room temperature, with no obvious power fluctuation. The number of lasing lines is 31 within the 10-dB bandwidth, and the wavelength spacing is 0.63 nm. In addition, the average optical signal-to-noise ratio is up to 25.15 dB. Finally, narrower wavelength spacing is obtained by increasing the length of the PMF.

Wavelength-number-tunable multi-wavelength SOA fiber laser based on NPR effect

Abstract A wavelength-number-tunable multi-wavelength SOA fiber laser incorporating a double pass Mach–Zehnder interferometer (MZI) is experimentally demonstrated in this paper. Due to the nonlinear polarization rotation (NPR) effect of SOA, the intensity-dependent loss (IDL) is induced by the combination consisting of SOA and polarization devices to achieve stable multiwavelength output with ultra-narrow wavelength spacing. In addition, the degree of IDL can be controlled by adjusting PCs for the purpose of tuning the number of wavelengths. Stable multiwavelength output with power equality have been achieved at room temperature, which have no obvious power fluctuation. The wavelength spacing is ultra-narrow, which is as small as 0.081 nm, and the number of lasing lines is tuned from 168 to 250. However, due to the high noise figure of SOA, the optical signal-to-noise ratios (OSNR) is less than 8.85 dB.

Investigation of a multiwavelength thulium-doped fiber laser incorporating a two-mode fiber filter

A multiwavelength, thulium-doped, ring fiber laser was proposed and experimentally demonstrated. The laser was realized exploiting the cooperative effects of a two-mode fiber filter, nonlinear polarization rotation and the four-wave mixing induced by a section of a highly nonlinear fiber with a length of 150 m. By fine-tuning the polarization controllers, stable multiwavelength outputs with 11 lasing lines within the bandwidth of 10 dB were obtained in 60 min. The maximum wavelength shift and optical power fluctuation of the eleven-wavelength operation for the laser are 0.08 nm and 1.86 dB, respectively, and the wavelength interval and the number of lasing lines can be changed by adjusting the length of the two-mode fiber. Furthermore, the effects of the different experimental parameters such as the pump power, output coupling ratio, nonlinear phase shift and the extinction ratio of the filter on the output performance have also been carefully investigated.

Tunable multiwavelength erbium-doped fiber laser based on nonlinear optical loop mirror and birefringence fiber filter

A tunable multiwavelength erbium-doped fiber laser (MWEDFL) based on nonlinear optical loop mirror (NOLM) and tunable birefringence fiber filter (BFF) is proposed and demonstrated. By combination of intensity-dependent loss modulation induced by NOLM and pump power adjustment, the proposed laser can achieve independent control over the number of lasing lines, without affecting other important characteristics such as channel spacing and peak location. In addition, the laser allows wavelength tuning with both the peak location and the spectral range of lasing lines controllable. Specifically, the peak location of lasing lines can be controlled to scan the whole spectral range between adjacent channels of comb filter by adjusting the BFF. Moreover, the spectral range of lasing lines can be controlled by adjusting NOLM. This tunable MWEDFL may be useful for fiber-optic communication and fiber-optic sensing.

Spectral parameters of nonchain volume-discharge HF(DF) laser radiation

Spectral parameters of nonchain chemical hydrogen (deuterium)-SF6 mixture lasers are compared for the cases of pumping by a discharge with UV illumination from generators with inductive energy storage and by a runaway-electron preionized diffuse discharge (REP DD) formed in a nonuniform electric field. It is shown that high homogeneity of volume discharges formed in the laser medium allows an increase in the number of lasing lines. Therewith, intense cascade transitions appear in the laser spectra, and the lasing efficiency on HF (λ = 2.8–3.2 μm) and DF molecules (3.8–4.2 μm) reaches its ultimate value. It is shown that the REP DD in gas mixtures with SF6 is an efficient pumping method for HF(DF) lasers.

A nonlinear polarization rotation-based linear cavity waveband switchable multi-wavelength fiber laser

A nonlinear polarization rotation (NPR)-based linear cavity waveband switchable multi-wavelength fiber laser is proposed and demonstrated. The NPR effect effectively induced intensity-dependent loss that can alleviate mode competition and result in multi-wavelength generation at room temperature. By adjusting the polarization controllers, the two wavebands in the region of 1530 and 1550 nm can be switched efficiently and the number of lasing lines can be also adjusted flexibly.

Multiwavelength fiber ring laser using a gain clamped semiconductor optical amplifier

We demonstrate a novel multi-wavelength fiber ring laser based on a gain clamped semiconductor optical amplifier. The number of lasing lines can be tuned by adjusting the loss inside the cavity. The wavelength interval between the wavelengths is 100GHz. The proposed laser shows a stable operation with total intensity fluctuation for a single laser line within ±0.02dB at room temperature for a period of 30-minutes.

Medium-power erbium-ytterbium-codoped multiwavelength fiber laser

This paper describes the design and operation of a stable single-longitudinal-mode medium-power multiwavelength fiber ring laser at room temperature. Single-longitudinal-mode oscillation was achieved by using an unpumped polarization-maintaining erbium-doped fiber inside the cavity as a saturable absorber. To investigate the function of the saturable absorber, erbium-doped fibers with different erbium concentrations and lengths were used. The output characteristics of the laser were studied using a scanning Fabry-Perot spectrum analyzer of resolution 27 MHz and an optical spectrum analyzer of resolution 6.25 GHz. The total output power of the laser obtained was more than 100 mW. The minimum separation between lasing wavelengths for stable single-longitudinal-mode oscillations, number of lasing lines, tunability, and maximum available output power were also explored.

Stable multiwavelength erbium-doped fiber ring laser using self-lasing feedback

An effective approach to enhance the performance of a room-temperature multiwavelength fiber ring laser is presented. By introducing self-lasing feedback in conventional phase-modulation-based multiwavelength fiber ring lasers, the number of lasing lines is increased and the differences among the lasing lines are diminished. Stable multiwavelength lasing with numbers of lasing lines up to 17 within the 3-dB spectral bandwidth and with wavelength spacing as small as 0.2 nm is achieved.

Multiwavelength fiber laser using a multimode elliptical‐core erbium‐doped fiber

AbstractThis paper reports on a fiber laser constructed with an erbium‐doped fiber, which has an elliptical core that is single‐moded along the minor axis and multimoded along the major axis. The laser can simultaneously emit several stable lines at room temperatures. The maximum number of lasing lines obtained depends on the number of modes supported by the erbium‐doped fiber in the cavity. The separation between the lasing lines depends on the fiber birefringence. The principle of operation is based on the anisotropic‐gain effects in a polarization‐maintaining fiber. The stability of the lasing lines, in the presence of anisotropic‐gain effects in a polarization‐maintaining fiber, has been explored. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 124–128, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20227

Model of a multiple-line distributed-feedback dye laser.

The theoretical basis for simultaneous oscillation of 2N - 3 laser lines is due to interference of N (for all even N > or = 2) pump beams in a distributed-feedback dye laser is described. Multiple gratings are produced in a dye solution by interference patterns of N/2 pairs of a frequency-doubled Nd:YAG laser. N/2 pairs of mutually time-delayed pulses induce multiple gratings of different periodicities, of which 2N - 3 gratings support oscillation of 2N - 3 lines and the remaining gratings, because of their larger periods, cannot support Bragg scattering. The maximum number of laser lines depends on the mutual delay between adjacent pairs of beams, coherence, states of polarization, pulse lengths, and of course the number of pulses. For three pairs of excitation beams derived from the same source through wave-front or amplitude phase division techniques, the output lasing lines varied from a minimum of three to a maximum of nine. This research was carried out by pumping of a dye solution with two, four, and six pulses, but the principle may be extended to multiple output lines, depending on the number of pump pulses and on the gain of the dye solution.

A five line distributed feedback dye laser

A multiple grating distributed feedback dye laser is described where laser emission is produced in a dye solution by the interference patterns of two pairs of frequency doubled Nd:YAG laser beams. Two pairs of pulses can induce five gratings that support oscillation of five lines and three pairs of pulses are expected to induce nine lines. The maximum number of laser lines depends upon the number of pump pulses and the time delay between the adjacent pairs of beams. For two pairs of excitation beams, derived from the same source through wave-front or amplitude phase division techniques, the output lasing lines varied from two to a maximum of five as the delay between the pairs of pump pulses is varied.

Multiwavelength fiber laser using a Sagnac loop filter

AbstractA Sagnac interferometer has been used in the ring cavity to produce a multiwavelength fiber laser. The results show that an elliptical‐core erbium‐doped fiber can produce more stable lasing lines compared to a normal erbium‐doped fiber. The principle of operation is based on polarization‐dependent gain phenomena in erbium‐doped fiber. The number of lasing lines and stability may be adjusted by using a polarization controller to control the polarization of the wave inside the cavity. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 200–202, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10719

On-line monitoring of biogenic isoprene emissions using photoacoustic spectroscopy

Isoprene (C5H8) is one of the most important biogenic volatile organic compounds (VOCs) in the atmosphere. To calculate the impact of isoprene on atmospheric processes models have been developed that describe the isoprene release from plants. Measurements of this release require techniques for a fast, sensitive, on-line isoprene detection. Photoacoustic (PA) spectroscopy is applied here for the first time to monitor biogenic isoprene emissions. A CO overtone PA spectrometer is used for the detection, probing the C-H stretching vibrations in the 3 to 4 μm range. This allows us to detect isoprene down to a few ppb with a time resolution of one minute in a continuous gas flow. The number of laser lines can be adjusted to meet the requirements of the respective experiment in terms of time resolution and selectivity against other possibly interfering VOCs. This results in a highly versatile instrument for the isoprene detection in biological experiments. Furthermore, the infrared fingerprint offers the potential to detect different isoprene isotopomers simultaneously, thus allowing us to carry out on-line labelling experiments. The new apparatus was used to study the light dependence of isoprene emission from Eucalyptus globulus. The results demonstrate, that the detector system is a promising tool for the study of plant gas emissions. It allows the validation of existing emission models which are important for atmospheric processes.

Experimental study of continuous wave hydrogen-fluoride chemical laser overtone performance

The overtone lasing performance of the supersonic continuous wave hydrogen-fluoride chemical laser at the University of Illinois at Urbana-Champaign was optimized by the same set of flow rates that optimized the fundamental performance. When the absorption/scattering losses of the mirrors were taken into account, an overtone efficiency (the ratio of overtone power to maximum fundamental power for the same flow conditions) of 70-90% was achieved. The overtone efficiency was a strong function of medium saturation. There was no significant change in overtone power and efficiency as the mode volume increased. However, there was an increase in the number of lasing lines and a shift to higher rotational (J) lines. Overtone performance was as sensitive to cavitypressure as fundamental performance was

Laser Emission Lines and Materials

This paper contains data on many of the laser materials reported in the literature up to May 1964. The first section contains a list of laser emission lines arranged according to increasing wavelength along with the corresponding active ion and host material. The second section contains information on parameters pertinent to laser performance. In both sections each line is referenced. No attempt has been made to include the wavelengths generated by second harmonics or the Raman effect. In this tabulation the total number of laser lines considered is 357. These lines originate from 65 laser systems. It is hoped that this catalog will be of special use to research workers in the life sciences who may not be familiar with the range of laser frequencies now available.