Laser Output Wavelength Research Articles

Effect of the operating characteristics parameters on the performance of a waveguide CO<sub>2</sub> laser

In this paper, the influence of the operating parameters on the performance of a waveguide-CO 2 laser was investigated. The output power versus discharge current, gas pressure, and gas mixture ratio were measured using a different tube design. Also, it is observed that the laser output wavelengths vary as the discharge current changes. The obtained maximum powers are ∼14.5 W in a tube of diameter 3 mm and length 70 cm at the pressure 50 mbar, using the active medium with two discharge regions.

Ring-resonator-integrated tunable external cavity laser employing EAM and SOA

We propose and demonstrate a tunable external cavity laser (ECL) composed of a polymer Bragg reflector (PBR) and integrated gain chip with gain, a ring resonator, an electro-absorption modulator (EAM), and a semiconductor optical amplifier (SOA). The cavity of the laser is composed of the PBR, gain, and ring resonator. The ring resonator reflects the predetermined wavelengths into the gain region and transmits the output signal into integrated devices such as the EAM and SOA. The output wavelength of the tunable laser is discretely tuned in steps of about 0.8 nm through the thermal-optic effect of the PBR and predetermined mode spacing of the ring resonator.

Enhanced laser characteristics of pyrromethene 650 using modified PMMA as solid hosts

Solid-state samples based on modified polymethyl methacrylate (MPMMA) with methanol doped with the dye pyrromethene 650 (PM650) are prepared. The effects of a volume percentage of methanol on the laser characteristics of the sample, including spectra properties, slope efficiency, photostability and tunable properties, are investigated. The broadband dye laser output wavelength is around 655 nm and a highest slope efficiency of 32.23% is achieved. Pumping the samples at a repetition rate of 5 Hz with a pulse energy of as high as 100 mJ (the fluence is 0.26 J/cm2), the longest lifetime (168000 shots) is obtained in the sample (MMA:methanol=18:2), and the corresponding normalized photostability reaches 109.19 GJ/mol. When the sample (MMA:methanol=18:2) is placed in a Shoshan-type oscillator, the narrow-linewidth operation is a continuous tuning range (up to 64 nm). The results indicate that the laser characteristics of solid-state dyes can be greatly enhanced by using modified PMMA with methanol serving as the solid host.

Solid-state dye lasers based on PMMA co-doped with PM597 and PM650

In order to enhance the laser performances, solid-state samples based on polymethyl methacrylate (PMMA) co-doped with pyrromethene 597 (PM597) and pyrromethene 650 (PM650) were prepared. With SHG of Q-switched Nd:YAG laser (532 nm, ∼15 ns) pumping the samples, laser emission from the mixtures of PM597 and PM650 both in liquid solution and incorporated into solid polymeric matrices were investigated. The highest slope efficiency of co-doped solid-state dye samples 30.8% was achieved. Through the dye PM650 being co-doped into the dye PM597, the dye laser output wavelength was extended for the existence of energy transfer from the dye PM597 to the dye PM650.

Design and performance analysis of a tunable and self-pulsation diode pumped double-clad D-shaped Yb<sup>3+</sup>-doped silica fiber laser

A wide range of applications have emerged for tunable ytterbium fiber lasers as single-frequency sources for spectroscopic applications, pumping source of Pr:ZBLAN amplifier, and Tm:ZBLAN upconversion laser, material processing, and military applications. In this paper, a 975-nm high power fiber coupled high power diode laser module of up to 5 W end pumping a ytterbium-doped multimode D-shaped fiber laser has been investigated. This used a Fabry-Pérot cavity with output coupler reflectivities of 80%, 60%, and Fresnel reflection of 4%. The output laser wavelength was tuned over a wide range of more than 50 nm, from 1041 to 1094 nm for cavity lengths from 1 to 10 m, respectively. An optical-to-optical slope efficiency of 45% was found for a 1-m cavity length, which increased to 60% for a 4-m cavity length. The maximum slope efficiency of 82.1% for a cavity length of 2 m was measured with the Fresnel reflection output coupler, and the measured lowest threshold pump power for this high gain cavity configuration was 130 mW. The threshold lasing pumping powers of 4.3, 4.5, and 4.7 W were dependent on the output coupler reflectivities of 80%, 60%, and Fresnel reflection of 4%, respectively. Also, self-pulsation phenomena were observed only at higher level pumping powers of more than 4 W and at longer cavity length.

High pulse energy output from tunable solid-state dye laser based on MPMMA doped with PM567

Tunable solid-state dye laser sample based on modified polymethyl methacrylate (MPMMA) with methanol co-doped with pyrromethene 567 (PM567) and Coumarin 440 (C440) was prepared. Tunable dye laser output wavelength from 546 to 594 nm was obtained in an oscillator-amplifier configuration. With the input seed laser energy being about 1.5 mJ, the highest dye laser output energy reached 113.9 mJ, and the corresponding conversion slope efficiency was 51.39%. To the best of our knowledge, the tuning range and narrow linewidth dye output energy is the best under the same condition so far. The linewidth for the seed laser and amplified laser were measured with the result of less than 0.2 nm. With the amplified medium being pumped at a repetition rate of 10 Hz with a pulse energy as high as 120 mJ (the fluence was 0.42 J/cm2), the laser output energy dropped to half of its initial value after approximate 43000 pulses.

Tunable Tm-doped fiber ring laser operating at 19 μm band using force-induced fiber grating as wavelength tuner

We report wavelength-tunable operation of a Tm-doped silica fiber laser by using a force-induced long-period fiber grating (LPFG) formed in a fiber ring resonator. The laser output wavelength is tuned by moving the transmission passband that is generated between adjacent resonance wavelengths due to the force-induced LPFG. By changing the grating period around 900 μm, we control the laser output wavelength between 1845 and 1930 nm.

Analytical model for the tuning characteristics of static, dynamic, and transient behaviors in temperature and injection current of DFB laser diodes

From the tuning mechanism of the DFB laser diode, we establish an analytical model for current and temperature tuning characteristics. The parameters of the model are identified by experimental results. The model is used to analyze the four DFB diode lasers, and the transient characteristics of the lasers are obtained. We also obtain the static characteristics of these lasers from Agilent 86142B Spectrometer. The comparison between the two values indicates that the correlation coefficients are both more than 0.9999. At the same time, according to the absorption spectrum of CO2 gas, we also measure the emission wavelength of lasers. Comparing it with the HITRAN spectrum of CO2 absorption lines, the two errors are shown to be within 3pm. The analytical model can accurately predict the transient output wavelength of lasers in tuning, the accuracy can meet the spectrum, optical coherence measurements and other practical requirements.

Dependence of Er:Yb-codoped 15μm amplifier on wavelength-tuned auxiliary seed signal at 1μm wavelength

We report on experiments performed with a cladding-pumped single-mode Er:Yb-codoped single-frequency fiber amplifier simultaneously seeded by a distributed-feedback diode at 1556 nm and a tunable external-cavity diode laser emitting at a wavelength of about 1 μm wavelength. The influence of the output wavelength of the external-cavity laser on amplification and reabsorption behavior of the Yb emission as well as the amplifier performance at a wavelength of 1556 nm is examined experimentally.

Application of a Tunable-Diode-Laser Absorption Diagnostic for CO Measurements in an Automotive HCCI Engine

An infrared laser absorption technique has been developed to measure in-cylinder concentrations of CO in an optical, automotive HCCI engine. The diagnostic employs a distributed-feedback, tunable diode laser selected to emit light at the R15 line of the first overtone of CO near 2.3 {micro}m. The collimated laser beam makes multiple passes through the cylinder to increase its path length and its sampling volume. High-frequency modulation of the laser output (wavelength modulation spectroscopy) further enhances the signal-to-noise ratio and detection limits of CO. The diagnostic has been tested in the motored and fired engine, exhibiting better than 200-ppm sensitivity for 50-cycle ensemble-average values of CO concentration with 1-ms time resolution. Fired results demonstrate the ability of the diagnostic to quantify CO production during negative valve overlap (NVO) for a range of fueling conditions.

Discretely tunable micromachined injection-locked lasers

This paper reports a micromachined injection-locked laser (ILL) to provide tunable discrete wavelengths. It utilizes a non-continuously tunable laser as the master to lock a Fabry–Pérot semiconductor laser chip. Both lasers are integrated into a deep-etched silicon chip with dimensions of 3 mm × 3 mm × 0.8 mm. Based on the experimental results, significant improvements in the optical power and spectral purity have been achieved in the fully locked state, and optical hysteresis and bistability have also been observed in response to the changes of the output wavelength and optical power of the master laser. As a whole system, the micromachined ILL is able to provide single mode, discrete wavelength tuning, high power and direct modulation with small size and single-chip solution, making it promising for advanced optical communications such as wavelength division multiplexing optical access networks.

Large-area organic distributed feedback laser fabricated by nanoreplica molding and horizontal dipping

The fabrication of visible wavelength vertically emitting distributed feedback (DFB) lasers with a subwavelength grating fabricated by a replica molding process and an active polymer layer printed by a horizontal dipping process is reported. The combined techniques enable the organic DFB laser to be uniformly fabricated over large surface areas upon a flexible plastic substrate, with an approach that is compatible with roll-based manufacturing. Using a fixed grating period and depth, DFB laser output wavelength is controlled over a 35 nm range through manipulation of the waveguide layer thickness, which is controlled by the speed of the horizontal dipping process. We also demonstrate that the active area of the structure may be photolithographically patterned to create dense arrays of discrete DFB lasers.

A single-longitudinal-mode CW 0.25 mm Tm,Ho:GdVO4 Microchip Laser

A single-longitudinal-mode of 0.25 mm Tm,Ho:GdVO4 Microchip Laser was reported. The maximal continuous wave (CW) output power was 26.4 mW and the threshold of 118 mW. The Tm,Ho:GdVO4 Microchip Laser output wavelength was centered at 2039.7598 nm with bandwidth of about 57.1 pm. The beam quality factor was M 2 ∼ 1.52 ± 0.03 measured by knife-edge method. The Longitudinal-Mode was scanned by a FPI and the transverse mode was monitored by an infrared vidicon camera.

Characteristics of Er and Er–Yb–Cr doped phosphate microsphere fibre lasers

In this paper both Er and Er–Yb–Cr doped phosphate microspheres have been successfully created through precise melting of the ends of fibre tapers, drawn, respectively, from Er and Er–Yb–Cr doped phosphate glasses. When coupled with a fibre taper, a microsphere fibre laser cavity can thus be configured creating a system pumped by a 980 nm laser diode and using an optical spectrum analyzer to monitor the spectral characteristics of the laser output. The performance and characteristics of the Er and Er–Yb–Cr microsphere lasers thus created are discussed in detail and cross-compared in this paper. Both lasers have shown low-threshold in terms of the pump power and the laser output wavelengths and a close investigation of the system has shown that the output power and laser stability are closely related to the size of the microsphere, the pump power and the microsphere material composition.

Theoretical prediction on the wavelength–temperature shift in pulsed TE CO 2 lasers

The wavelength–temperature shift observed in pulsed TE CO 2 lasers is discussed theoretically by means of Six-temperature model rate equations for tunable TE CO 2 lasers. Numerical calculations of the temperature–wavelength shift in a pulsed TE CO 2 laser with a simple plano-concave stable resonator, whether excited by conventional low-inductance fast-discharge scheme or by a long-pulse Pulser/sustainer discharge scheme, show that the laser output wavelengths are within the 10P branch as the ambient temperature varies from 228 to 338 K, but will change as the ambient temperature varies. The laser output wavelengths will move to the transition lines with longer wavelengths in the 10P branch as the ambient temperature increases and vice versa. The calculated results also illustrate that near the ambient temperature of 310 K, the laser is more likely to operate on multi-transition lines. Considering this wavelength–temperature shift, the chilling device adopted in high-power high repetition rate TE CO 2 lasers is important in maintaining a stable laser output spectra as well as a stable laser output power. The numerical results also suggest that a frequency agile resonator is highly recommended if stable laser output spectra are required in TE CO 2 lasers.

All-fiber Tm-doped double-clad fiber laser with multi-mode FBG as cavity

An all-fiber LD-clad-pumped Tm-doped fiber laser was reported, and the CW maximal output power reached 24 W at nearly 1.94 μm. The double-clad Tm-doped fiber had a demission of 25/250 μm with the core NA 0.1 and inner-clad NA 0.46. A matched passive multi-mode FBG acted as the front cavity. Cooling by the water, the 56% high slope efficiency was achieved and threshold was 6.4 W, respected to the launched pump power. At the low power pump, the fiber laser spectrum had only one peak at 1.936 μm. Increasing the launched pump power, the output laser wavelength grew to 3–4 peaks. Because the multi-mode FBG reflectivity was not very high, both ends of the fiber laser had laser output power, and the ratio was nearly 10:1.

Frequency stabilization in FBG external cavity semiconductor laser based on acetylene absorption method

A frequency-stabilized 1.53 Open image in new window FBG external-cavity semiconductor laser by using acetylene absorption is presented and its basic principles are introduced. Graded refractive index fiber and pigtailed fiber are used in the absorption air chamber to enhance the coupling stability. The impact of the background power is eliminated by using the third-harmonic mode-locking technique. A lock-in amplifier is utilized to ensure that the output laser wavelength is locked at the C2H2 absorption line of 1530.37 nm. The frequency stability reaches 10−8 within 24 h.

Performance of a wavelength-tunable erbium-doped fiber laser using a Sagnac interferometer

We experimentally demonstrate a wavelength-tunable erbium-doped fiber laser that is composed of a ring cavity and a single-mode fiber Sagnac interferometer in a new and simple arrangement. We find that the fiber laser output wavelength is tunable by adjusting the filter effect of the Sagnac fiber loop through a fiber polarization controller set there. The quasi-single-wavelength continuously tunable laser outputs could be achieved within some wavelength range. The multi-wavelength laser outputs could also be observed under some appropriate settings of the polarization controller. A theoretical demonstration of the wavelength tunability about the transmission-type Sagnac loop filter has also been achieved using the Jones calculus theory.

Phase-locked laser system for a metastable states qubit in ^40Ca^+

We describe the development of a phase-locked laser system tailored to an ion-trap-based quantum information processor with (40)Ca(+). Laser outputs from an extended cavity diode laser and a Ti:sapphire laser with output laser wavelengths of approximately 850 and 854 nm, respectively, were phase locked and used to excite a Raman transition between the D(3/2) and D(5/2) metastable states qubit. Development and the performance of the laser system are described. We also compare the characteristics and the benefits of the developed qubit coupling with those in the conventional approaches.

Tunable self-seeded multiwavelength Brillouin-Erbium fiber laser with enhanced power efficiency

We have demonstrated a tunable multiwavelength Brillouin- Erbium fiber laser (BEFL), which is internally self-excited without additional Brillouin pump. With the use of a birefringence loop mirror filter, the laser output wavelength can be tuned through modifying the filtering profile of the birefringence filter. As a result, the generation of more than 70-wavelength combs with uniform power distribution has been obtained in ~11-nm tuning range. And the wavelength of combs can be tuned in the bandwidth of the Sagnac loop filter. Also, utilizing the spare port of the 3-dB coupler as the output port, the laser output power efficiency has been enhanced by 13 dB.