Virtual Journal of Laser

Silicon nitride (SiN) microdisk resonators with a 40-nm horizontal air slot and a nanocrystal Si (nc-Si) emitting top layer are investigated. The whole structure is fabricated using only a single deposition and lithography step, with the light-emitting layer self-aligned to excite the slot-mode within the air slot. The nc-si are excited via top-pumping using a UV laser diode, and the visible light emission from nc-Si is coupled into the whispering gallery mode (WGM) with the light concentrated in the air slot. The WGM resonances are observed via side-photoluminescence setup using a Si charge-coupled device. The feasibility of applying this structure as a biosensor is demonstrated, with an estimated surface sensitivity of 2.8 nm/nm.

A novel frequency stabilization method for external cavity diode lasers by using an all-pass polarization-split Sagnac loop is proposed. This scheme uses a quarter waveplate to convert the incident beam to a circularly polarized beam, and a polarization beam splitter for the input and output of the Sagnac loop. The two beams with perpendicular polarizations counter-propagate in the loop and experience different absorption of the Rb cell; therefore, the Sagnac loop output beam is converted into elliptical polarization. The dispersion phase shift induced by Rb saturation absorption can be obtained by balanced polarization-divided detection of the Sagnac loop output beam. The experimental results showed the feasibility and merits of the new method. This scheme is simple, robust, low-cost, and has potential applications in atomic physics experiments.

A novel complex-coupled distributed feedback quantum cascade laser emitting around
$lambdasim 4.7~mu{rm m}$ is demonstrated by a sampled Bragg grating (SBG). The key superiorities are to utilize the
${+}{1}{rm st}$-order (positive first order) transmission of the SBG for laser single-mode operation, and use conventional holographic exposure combined with the optical photolithography technology to fabricate the sampled grating, which lead to improved flexibility, repeatability, and cost-effectiveness. Selective single-mode lasing with a mean side mode suppression ratio above 20 dB and wavelength coverage range of 87 nm is achieved by changing the sampling period.

A stable and switchable dual-wavelength polarization-maintaining erbium-doped fiber ring laser is proposed and demonstrated experimentally by using a novel filter, which is formed from dual-pass Mach–Zehnder interferometer incorporating a sagnac loop. By adjusting the polarization controllers, the output laser can be switched between single- and dual-wavelength. The wavelength spacing of the dual-wavelength can be tuned from 0.084 to 4.26 nm. Its 3-dB bandwidth and side mode suppression ratio are less than 0.015 nm and higher than 64 dB, respectively. In addition, the peak power fluctuation and wavelength shift are monitored to be less than 0.5 dB and 0.01 nm during an hour, respectively. The characteristics of the novel filter in experimental measurement accord with the result of theoretical analysis.

We present a new and simple method for the fabrication of carbon nanotube (CNT) films for fiber laser mode-locking. Using a microtip, we deposited a droplet of CNT/polymer suspension directly onto a fiber ferrule. Typical film thicknesses as low as 20
$mu{rm m}$ are measured. Thicker films are easily achievable through the deposition of additional droplets, which allow for fine tuning the transmittance of the film. Based on a 40-mg/ml CNT concentration film used in an Erbium-doped fiber laser, we obtain mode-locked pulses with a bandwidth of 10.2 nm and duration of 364 fs.

Phase error variance is an important figure in many laser applications such as coherent optical communication and interferometric optical diagnosis and is directly related to system performance. In this letter, we show that the phase error variance of a single-mode laser with a narrow linewidth can be measured as a function of relative delay without using any reference (local) beam. In addition, the results are in good agreement with those measured using the beat note of two identical lasers, one of which acts as a local beam. The new method, uniquely we believe, enables us to evaluate the phase error variance of lasers at continuous delays without using any reference (local) beam.

We present a gold-to-gold bonding method that combines features of surface activated bonding and capillary bonding. The process is performed at a relatively low temperature of 150
$^{circ}{rm C}$ and therefore allows the integration of materials with highly mismatched coefficients of thermal expansion. In this letter, the potential of this technique is illustrated by assembling a high-power flip chip semiconductor disk laser utilizing a chemical vapor deposition diamond heat spreader. The laser produces up to 14 W of output power at 15
$^{circ}{rm C}$ gain element temperature with a nearly diffraction-limited output beam. Further scaling of bonding area to wafer-level could make this method useful in the packaging of various optoelectronic and microelectronic components.

We report highly reflective fiber Bragg gratings (FBGs) photoinduced in the core of Ce/Tm co-doped ZBLAN fibers using a 248-nm excimer laser. We compare the characteristics of the FBGs inscribed in ZBLAN fiber to those produced in silica fiber. We also characterize the strain and temperature responses of ZBLAN FBGs and find that the wavelength can be strain- and temperature-tuned at rates that are 45% and 15% higher, respectively, compared to silica FBGs.

In this letter, a monolithically integrated widely tunable optical receiver is demonstrated. A sampled-grating DBR (SG-DBR) laser, an optical 90-degree hybrid, four high-speed uni-travelling-carrier photodetectors and microstrip transmission lines are integrated on a single InGaAsP/InP chip. A 42-nm tuning range and a 35-GHz detector bandwidth are achieved. Experiments show real-time reception of 40 Gb/s BPSK data.

In this letter, we demonstrate an all-fiber Q-switch laser in erbium-doped fiber using an intracavity loss modulator that controls the power transmitted by a cladding mode. The cladding mode is coupled by a pair of concatenated long period gratings; pulsed regime is achieved by dynamic attenuation of the power transmitted by the cladding mode, and attenuation is caused by lateral compression with a piezoelectric transducer. The pulse sequence can be controlled from a single shot up to repetition rates of 2 kHz. The laser performance is analyzed as a function of the pump power and emission frequency; pulses having a peak power of 4 W and a duration of
${sim}{rm 80}~{rm ns}$ can be generated with an absorbed pump of 100 mW.