Half-maximum Spectral Width Research Articles

High power GaInNAs superluminescent diodes emitting over 400 mW in the 1.2 μm wavelength range

A high-power superluminescent diode emitting over 400 mW in the 1.2 μm range is reported. The active region is based on a single GaInNAs/GaAs quantum well positioned within a low-confinement vertical waveguide and a lateral ridge waveguide geometry, ensuring single transverse mode operation. The peak wall-plug efficiency and the differential efficiency in the linear region were 22.8% and 0.38 W/A, respectively. The full width at half-maximum spectral width for the maximum output power was 22 nm, corresponding to a spectral power density of 19 mW/nm, a threefold increase compared to continuous wave superluminescent diodes based on a quantum dot active region operating in the same wavelength range. Besides exhibiting excellent optical and electrical properties, the GaInNAs active region enhances operation at elevated temperatures. In this respect, an output power of about 210 mW is demonstrated at operation temperatures as high as 60 °C, while 150 mW is still emitted at 70 °C. The unique combination of parameters demonstrated makes these GaInNAs QW-based superluminescent diodes particularly attractive for hybrid integration with silicon photonic circuitry, enabling the demonstration of compact solutions for sensing, optical coherence tomography, and other emerging concepts exploiting photonic integration technology and requiring single transversal mode operation, good efficiency, broadband high spectral power density, and uncooled operation at elevated temperatures.

Self-phase-locked divide-by-2 optical parametric oscillator as a broadband frequency comb source

We investigate, both theoretically and experimentally, spectral, temporal, and coherence properties of a degenerate synchronously pumped optical parametric oscillator (SPOPO) as a divide-by-2 subharmonic generator. Periodically poled lithium niobate was used as the nonlinear gain medium and 180 fs pulses from a mode-locked Ti:Sapphire laser as the pump. A regime of stable SPOPO operation at degeneracy was achieved, where the SPOPO longitudinal modes were phase-locked to the pump, even without active cavity-length stabilization. Phase locking was confirmed by interference measurements between the pump and the frequency-doubled optical parametric oscillator output, as well as by beat frequency measurements using an independent continuous-wave laser. We have found that the stability range of such a phase-locked state, with respect to external perturbations, increased with the pump power and decreased with the cavity Q at a constant number of times above threshold, in excellent agreement with our model based on coupled nonlinear wave equations. At degeneracy (around 1550 nm), the SPOPO produced 70 fs output pulses with the full width at half-maximum spectral width of 210 cm−1, which manifests significant pulse compression and spectral broadening with respect to the pump laser.

Response of Axially Stressed Edge-Illuminated Holographic Gratings in PQ/PMMA Photopolymers

A free-space unslanted, edge-illuminated, tunable Bragg filter in Phenanthrenquinone doped Poly(methyl methacrylate) (PQPMMA) operating at 1550 nm has been realized with a tuning range larger than 4 nm. The grating is ~1 cm long with a rejection efficiency of ~90% and a full-width at half-maximum spectral width of ~0.35 nm in its unstressed state. The tunability of the grating was achieved by stretching and compressing the sample.

Influence of Separate Confinement Heterostructure on Emission Bandwidth of InGaAsP Superluminescent Diodes/Semiconductor Optical Amplifiers With Nonidentical Multiple Quantum Wells

Experiments show that the layer of separate confinement heterostructure (SCH) has a significant influence on the emission spectrum of superluminescent diodes (SLDs)/semiconductor optical amplifiers (SOAs). Reducing the thickness of SCH layer at the p-side could improve the uniformity of carrier distribution among multiple quantum wells (MQWs). With three In/sub 0.67/Ga/sub 0.33/As/sub 0.72/P/sub 0.28/ QWs near the p-side and two In/sub 0.53/Ga/sub 0.47/As QWs near the n-side, when the thickness of the SCH layer changes from 120 to 30 nm, the operation current for SLDs/SOAs to exhibit the full-width at half-maximum spectral width of above 270 nm could be reduced from 500 to 160 mA.

Extremely broadband AlGaAs/GaAs superluminescent diodes

Extremely broadband AlGaAs/GaAs superluminescent diodes are fabricated on substrate with four quantum wells of different widths. By choosing 20, 33, 56, and 125 Å, respectively, for the four quantum wells, the spectrum could be broadened to several times that of the conventional superluminescent diodes. The measured spectra of the fabricated devices with such quantum-well structure show that the full-width at half-maximum spectral width could be as large as 915 Å.

Integrated concave grating WDM demultiplexer with0.144 nm channel spacing

A 60-channel WDM demultiplexer based on a concave grating with 0.144 nm channel spacing in the 1.5 µm wavelength region was fabricated. The demultiplexer comprises SiO2/SiON/SiO2 waveguides on Si and an individual channel has a full width at half maximum spectral width of 0.09 nm.

Optical pumping of Rb vapor using high-power Ga1-xAlxAs diode laser arrays.

The use of high-power ${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Al}}_{\mathit{x}}$As diode laser arrays for optical pumping of Rb vapor has been examined both theoretically and experimentally. Our studies show that large atomic polarizations can be obtained using the broad spectral output of a diode laser array if the Rb resonance line is collisionally broadened by several atmospheres of a buffer gas. The objective was to study the effectiveness of diode laser arrays as light sources for optically pumped spin-exchange polarized $^{3}\mathrm{He}$ targets. The average Rb polarization was deduced at three different Rb vapor pressures using the polarization induced in the $^{3}\mathrm{He}$ buffer gas. The largest $^{3}\mathrm{He}$ polarization observed was 53% using a 20-W diode array with 1.9-nm full width at half maximum spectral width in 10.5 amagat of $^{3}\mathrm{He}$. This result compares favorably with other light sources for this target. The measured average Rb polarizations are compared to theoretical calculations.