Laser Diode Amplifier Research Articles

Two-photon fluorescence bioimaging with an all-semiconductor laser picosecond pulse source

We have demonstrated successful two-photon excitation fluorescence bioimaging using a high-power pulsed all-semiconductor laser. Toward this purpose, we developed a pulsed light source consisting of a mode-locked laser diode and a two-stage diode laser amplifier. This pulsed light source provided optical pulses of 5 ps duration and having a maximum peak power of over 100 W at a wavelength of 800 nm and a repetition frequency of 500 MHz.

High resolution FROG system for the characterization of ps laser pulses

We report on a frequency resolved optical gating (FROG) system which allows the reconstruction of amplitude and phase of picosecond pulses generated by mode-locked diode laser oscillators and amplifiers. The main challenge of developing such a FROG system is the required high spectral resolution. In the spectrometer a cylindrical grating with 1200 lines/mm and a radius of curvature of 3 m is used. A width of the illuminated area of 15 cm provides in a spectral resolution exceeding 2 GHz (1.4 pm) at 460 nm. The FROG system is, thus, well suited for analyzing ps-pulses with durations of up to 80 ps and a corresponding fourier-limited spectral width of 0.017 nm.

Efficient noise suppression of an amplified diode-laser by optical filtering and resonant optical feedback

We present the noise suppression of an amplified diode laser by using an optical filter and resonant optical feedback. The intensity noise of the amplified diode laser has been significantly decreased by using the optical filter cavity. It was further suppressed and reached the shot noise limit at 15 MHz by introducing resonant optical feedback from the transmission of the filter cavity. The filter cavity transmits 53% of injection power, and the output power of the filter cavity is more than 200 mW. The observed frequency fluctuations were less than 100 kHz in one minute. This level of noise suppression and output power may allow diode lasers to be utilized in many quantum-optics experiments.

Synchronous photoinjection using a frequency-doubled gain-switched fiber-coupled seed laser and ErYb-doped fiber amplifier

Light at 1560 nm from a gain-switched fiber-coupled diode laser and ErYb-doped fiber amplifier was frequency doubled to obtain over 2 W average power at 780 nm with $\ensuremath{\sim}40\text{ }\text{ }\mathrm{ps}$ pulses and pulse repetition rate of 499 MHz. This light was used to drive the 100 kV DC high voltage GaAs photoemission gun at the Continuous Electron Beam Accelerator Facility at Jefferson Laboratory to produce a high average current beam ($100\text{ }\text{ }\ensuremath{\mu}\mathrm{A}$) of highly spin-polarized electrons ($>80%$). This new drive-laser system represents a significant advance over laser systems used previously, providing significantly higher power and enhanced reliability.

600 mW optical output power at 488 nm by use of a high-power hybrid laser diode system and a periodically poled MgO:LiNbO3 bulk crystal

600 mW second-harmonic blue light at 488 nm has been generated by use of a master-oscillator power amplifier diode laser system as a pump source with a maximum optical output power of 4 W in continuous-wave operation. For frequency doubling, a periodically poled MgO:LiNbO3 bulk crystal was used in a single-pass configuration. A conversion efficiency of 15% and an overall wall-plug efficiency of 4% were achieved.

Generation of two-mode bright squeezed light using a noise-suppressed amplified diode laser

We present the generation of nonclassical state using an amplified diode laser as a light source. The intensity noise of an amplified diode laser was significantly suppressed and reached the shot noise limit at 15 MHz using both a filter cavity and resonant optical feedback. Frequency doubling efficiency of 66% and up to 120 mW output power of green has been achieved in cw second-harmonic generation from 1080 nm to 540 nm. Bright two-mode amplitude-squeezed state was generated from a type-II nondegenerate optical parametric amplifier pumped by generated green light. The measured noise reduction is 2.1+/-0.2 dB below the shot-noise level.

Efficient suppression of diode-laser phase noise by optical filtering

We show that the excess phase noise of an amplified diode laser can be efficiently suppressed by double passage through a high-finesse cavity. The cavity transmits 18% of the injected optical power in double pass and reduces the power spectral density of excess phase noise at 1 MHz by 85 dB. If the filtered light is homodyned with a coherent state of light on a 50–50 beam splitter, the intensity noise of the emerging field in one port cannot exceed the shot-noise level by more than 0.022 dB at 1 MHz for 1 mW of optical power. This level of noise suppression may allow diode lasers to be used in phase-noise-sensitive experiments.

A single to multi-wavelength converter using Fabry–Perot laser diode with linear optical amplifier and its applications to the wavelength division multiplexing-passive optical network system

We propose and demonstrate a novel single to multi-wavelength converter using a Fabry–Perot laser diode (FP-LD) and linear optical amplifier (LOA) which is based on the cross gain modulation (XGM). It can convert an input signal to many wavelengths simultaneously. Multi-modes of the FP-LD were used for probe signals and the LOA was used with the cross gain modulation medium effect. Moreover, we propose a wavelength division multiplexing passive optical network (WDM-PON) link employing multi-wavelength converter for broadcasting function. A spectrally sliced FP-LD is used as a wavelength-locking optical source and multi-wavelength converter is used for broadcasting signals. The down stream transmission of 2.5Gbps is performed over 30km. We verified feasibility of it as a WDM-PON optical source.

Broadband InGaAs tapered diode laser sources for optical coherence radar and coherence tomography

This letter reports on broadband laser sources based on InGaAs tapered diode laser amplifiers with external optical feedback. The generated 920nm radiation with a bandwidth of up to 20nm and a power of a few hundred milliwatts is emitted in an almost diffraction limited beam. Spectral filtering and subsequent amplification in a second tapered amplifier provides radiation with spectral widths in the range of 20to40nm and optical output powers of up to 2.5W.

Theory and experiments of a mode-beating noise-suppressed and mutually injection-locked Fabry-Perot laser diode and erbium-doped fiber amplifier link

By using Fabry-Perot laser diode (FPLD) as a resonant ultranarrow bandpass filter in an Erbium-doped fiber amplifier or laser (EDFA or EDFL), the theory and experiment for side-mode suppression and linewidth reduction of mutually injection-locked EDFL-FPLD and EDFA-FPLD links are demonstrated. Based on the amplified feedback injection loop, the 3-dB linewidth of 3.4 MHz for the EDFA-FPLD link is determined by using self-heterodyne interferometric spectral analysis. The EDFA-FPLD link exhibits a nearly mode-beating noise-free performance as compared to the EDFL-FPLD link. This is due to the release of the resonant cavity configuration in the EDFL-FPLD link at a cost of slightly lower side-mode suppression ratio (/spl sim/42 dB). The maximum output power of the EFDA-FPLD link is 20 mW under an FPLD input power of 0.1 mW.

Lateral resolution of 28 nm (λ /25) in far-field fluorescence microscopy

We demonstrate sub-diffraction lateral resolution of 28±2 nm in far-field fluorescence microscopy through stimulated emission depletion effected by an amplified laser diode. Measurement of the optical transfer function in the focal plane reveals a 6-fold enlargement of the spatial bandwith over the diffraction limit. The resolution is established by imaging individual fluorescent molecules on a surface. Corresponding to 1/25 of the responsible wavelength, the attained resolution represents a new benchmark in far-field microscopy and underscores the viability of fluorescence nanoscopy with visible light, conventional optics and compact laser systems .

High-power 457-nm light source by frequency doubling of an amplified diode laser.

We demonstrate the generation of 150-mW blue coherent single-mode radiation at 457 nm in a compact and inexpensive setup. The light is generated by frequency doubling the radiation of a master oscillator power amplifier (MOPA) system in an enhancement cavity with a potassium niobate (KNbO3) crystal. The MOPA consists of a 914-nm single-mode diode laser and a broad-area diode laser (BAL) as the amplifier. The BAL is a multimode laser with a specified wavelength of 938 nm. Sufficient gain at 914 nm is obtained by antireflection coating the BAL front surface and by cooling it to -10 degrees C.

Fabrication of periodically poled lithium tantalate for UV generation with diode lasers

Fabrication of periodically poled lithium tantalate (PPLT) with periods as short as 1.3 μm for second harmonic generation (SHG) in the UV range and for optical parametric oscillators pumped at 532 nm is reported. Both the maximum crystal size of up to 40 mm and the minimum poling period of 1.3 μm are improvements on earlier results, achieved by optimizing the poling conditions and by using a novel electrode design consisting of electrode structures on both surfaces of the crystal. Single-pass SHG of a master oscillator power amplifier (MOPA) diode laser with an output power of 1.36 mW at 336 nm using a 16-mm-long PPLT crystal with a 1.5 μm poling period is reported.

Self-detection characteristics of the Sagnac frequency shift in a mechanically rotated semiconductor ring laser

Self-detection of the frequency difference between the two counter propagating oscillation frequencies in a mechanically rotated semiconductor ring laser (SRL) was successfully demonstrated. An SRL used for experiments consisted of a pig-tailed laser diode amplifier module. Detection characteristics of an SRL as an optical gyroscope were investigated and discussed. Beat frequency, which was detected by the terminal voltage change of an SRL without branching the circulating optical power, was measured as a function of the rotation rate, changing the loop radius for investigating the loop radius dependence on the detection sensitivity. The measured detection sensitivity characteristics coincided well with the theoretical prediction based on the Sagnac effect, and it was found that SRLs could be operated as optical gyroscopes. Furthermore, we verified that lock-in phenomenon was one of the most dominant noise sources in the S-RLG.

Analysis of cross-gain modulation wavelength conversion in tapered-waveguide laser-diode amplifiers

Analysis of cross-gain modulation wavelength conversion in tapered-waveguide laser-diode amplifiers

Fiber ring laser with flint glass fiber and its sensor applications

A new fiber ring laser has been proposed which is composed of a laser diode amplifier, a flint glass fiber as a sensing element, and a Faraday cell as a bias element, and applied to a frequency-domain sensor in which nonreciprocal effects such as current or rotation can be measured from a frequency change in the beat signal. A sign of current or rotation direction can be determined and a lock-in phenomenon is avoided owing to the bias element.

Sub-picosecond gain dynamic in highly index-guided tapered-waveguide laser diode optical amplifiers

The sub-picosecond gain dynamic in a highly index guided tapered-waveguide laser diode amplifier is studied. The analysis is based on a set of rate equations for the carrier density N and carrier temperature T, where the effects of lateral distributions of both N and T are considered. It is found that both N and T have significant effects on the gain dynamic of the tapered-waveguide laser diode amplifier. The gain saturation of the tapered-waveguide amplifier for both 20ps and 200fs pulses is also calculated.

Measurements and modeling of reflective bistability in 1.55-μm laser diode amplifiers

We present experimental measurements of bistable characteristics for the case of a 1.55-/spl mu/m symmetric Fabry-Perot laser amplifier with a particularly rich variety of behavior for reflected signals. Three main forms of hysteresis loops are observed on reflection. The hysteresis loop changes from anticlockwise to clockwise hysteresis in the optical output-input characteristic when the drive current or initial phase detuning is changed. A butterfly hysteresis loop is observed experimentally at an optical input power as low as 300 /spl mu/W for a drive current equal to 94% of the lasing threshold. The dependence of the reflective optical bistability on drive current, initial phase detuning, and injected optical pewter has been investigated for the first time in an uncoated 1.55-/spl mu/m amplifier. Measurements of the device voltage shifts on switching reveal hysteresis loops which match those in the corresponding optical powers and which indicate the amount of gain saturation and nonlinear refraction responsible for bistability. An analytical model is used to describe the observed reflective bistability and to give insight into the detailed physical mechanisms responsible.

Proposal of a semiconductor ring laser gyroscope

We proposed a novel optical inertial rotation sensor using a semiconductor ring laser (SRL). The frequency difference between the two counter propagating oscillation frequencies was automatically generated in a mechanically rotated SRL, which consisted of a pig-tailed laser diode amplifier module. And the Sagnac frequency shift could be detected at the first time as a beat note by the terminal voltage change of the SRL without branching the circulating optical power. These experimental results verify that an SRL operates as an optical inertial rotation sensor based on the Sagnac effect.

Experimental characterization and numerical modelling of an AlGaAs oscillator broad area double pass amplifier system

=1.1). The detailed experimental characterization includes the measurement of the output power as a function of the optical and electrical input power as well as the measurement of the dependence of the small signal gain, the saturation power and the power of the amplified spontaneous emission (ASE) on the amplifier current. The numerical analysis is based on a two-dimensional model which considers the spatial propagation and amplification of the input beam in the amplifier’s active layer and the gain competition between ASE and the amplified input radiation. The numerical simulation provides values for parameters measured in the experiment (such as the saturation power or the small signal gain) and the power distribution in the amplifying layer. The good agreement between the experimental and numerical results indicates that the phenomenological, steady-state description of the amplification process should be well suited for a simple and rapid analysis of basic properties of high-power diode laser amplifiers.