High-peak-power picosecond optical pulse generation from highly RF-modulated InGaAsP DH diode laser

The feasibility for generating high-peak-power ultrashort optical pulses was demonstrated from a highly RF-modulated InGaAsP DC-PBH laser diode at 1.3 ?m for the first time. Measured pulse width is found to be approximately 28 ps at 7 mW averaged output power, and peak output power reached about 1.2 W at 210 MHz repetition frequency. Higher peak output and shorter optical pulses could be expected with this type of semiconductor diode laser in the near-infra-red region.     

Self-Q-switched picosecond optical pulse generation with tandem-type AlGaAs TJS laser

Experimental results are presented for ultrashort optical pulse generation by an AlGaAs tandem-type laser with transverse junction stripe structure. The shortest optical pulse width of 14 ps was observed by an ultrafast streak camera, while typical pulse widths were about 20 ps. Further shorter pulses may be expected with this type of semiconductor laser by adequate control of the saturable absorber region.     

Bandwidth limited picosecond optical pulse generation from actively mode-locked AlGaAs diode laser

A simple configuration made of a conventional AlGaAs diode laser without antireflection coating combined with an external reflector and an optical etalon was proved to be practically feasible to generate bandwidth limited mode-locked optical pulses of 30 ps duration by synchronous modulation at the external cavity mode interval. Generated optical pulse shape was found to be Lorentzian rather than Gaussian for the first time, based on the measurements of both the s.h.g. correlation method and the ultrafast streak camera.     

Multiwavelength picosecond optical pulse generation using anactively mode-locked multichannel grating cavity laser

A multichannel grating cavity (MGC) InGaAsP-InP ridge diode laser is found to be suitable for multiwavelength ultrashort optical pulse generation using active mode-locking techniques. By using different configurations of the MGC laser, dual wavelength picosecond pulses are successfully produced with good spectral quality, either simultaneously or with a programmable relative delay between the channels. For a channel separation of 2.2 nm, pulses with a duration of 60 ps and a spectral width of 11.6 GHz have been obtained. The experimental results are compared with those from a theoretical analysis of the multiwavelength mode-locking process using a set of modified coupled-cavity rate equations. The minimum achievable pulsewidths generated by the actively mode-locked MGC laser are shown to be limited by the resolution bandwidth of grating used. The dependence of pulsewidth on RF drive frequency detuning is examined and it is found that the ultrashort pulses can be obtained over a wide range of frequency detuning. The interchannel cross-talk originating from gain saturation and carrier depletion is also discussed     

Dual-wavelength picosecond optical pulse generation using anactively mode-locked multichannel grating cavity laser

Picosecond pulse generation by active mode locking has been achieved simultaneously at two wavelengths using a multichannel grating cavity Laser. For a spectral channel separation of 2.2 nm, pulses of duration of 60 ps and with a spectral width of 11 GHz have been obtained. The pulse widths are limited by the spectral dispersion of the grating used     

More than 100-wavelength-channel picosecond optical pulse generation from single laser source using supercontinuum in optical fibres

A novel method for generating multiwavelength-channel picosecond optical pulses from a single laser source is proposed using supercontinuum in optical fibres combined with an all-fibre birefringent periodic filter. More than 100-wavelength-channel, 10 ps optical pulses are generated simultaneously over a 1.224-1.394 mu m spectral range with a 1.9 nm spacing using a 7.6 ps Nd:YLF laser pulse source.<>     

Multiwavelength 10-GHz picosecond pulse generation from asingle-stripe semiconductor diode laser

A single-stripe GaAs-AlGaAs semiconductor optical amplifier (SOA) has been used to generate four tunable wavelength-division multiplexed (WDM) channels simultaneously, each transmitting 12-ps pulses at 2.5 GHz, for an aggregate pulse rate of 10 GHz. Wavelength tuning over 18 nm has been demonstrated with channel spacing ranging from 0.8 to 2.1 nm. A potential spectral correlation across the multiwavelength spectrum has been studied in both experiment and simulation methods. These results show the potential for utilizing single stripe laser diodes as multiwavelength sources in WDM-TDM network     

100 GHz optical pulse generation using Fabry-Perot laser undercontinuous wave operation

Optical pulse generation at 100 GHz using a 1.5 μm Fabry-Perot laser is experimentally demonstrated under continuous wave operation. Although the output from the laser is almost constant, sub-picosecond short pulses at 100 GHz are obtained after propagation through a singlemode fibre. The measured radiofrequency spectrum confirms that the Fabry-Perot laser is passively modelocked     

Tunable picosecond pulse generation by an N2laser pumped self Q-switched distributed feedback dye laser

The temporal characteristics of a distributed feedback dye laser are investigated both theoretically and experimentally. It is shown that the feedback is provided by the gain modulation and that the effect of refractive index modulation is negligible. The solution of the coupled rate equations predicts the generation of picosecond pulses. The mechanism of short pulse formation is selfQ-switching which differs fundamentally from mode locking. A novel experimental arrangement for pumping the distributed feedback laser is described which makes it possible to obtain transform-limited pulses even with a partially coherent pumping source such as the N2laser. The experimental results show excellent qualitative and satisfactory quantitative agreement with the computer solutions. A very simple and reliable method for generation of tunable, nearly transform-limited single pulses with 36 ps duration (FWHM) is demonstrated experimentally. The feasibility of picosecond and subpicosecond pulse generation in the entire visible and near IR region is discussed.     

Study of optical phase conjugation in bulk traveling wave semiconductor optical amplifier

Optical phase conjugation (OPC) in a bulk SOA has been optimized both under static and dynamic conditions. Conjugation with gain has been obtained. Dynamic optimization leads to a compromise between conversion efficiency and signal-to-background (S/B) ratio, providing that the modulated signal is kept a minimum of 5 dB weaker than the pump to avoid detrimental saturation effects. Transparent 10-Gb/s phase conjugation with extinction ratio around 20 dB at moderate power levels is reported.     

Gyrotron traveling wave amplifier with out-ridged waveguide

The out-ridged waveguide is proposed for the use of gyrotrons operating at higher harmonics of electron gyrofrequency. Eigenvalues and the associated field components of the out-ridged waveguide are obtained with Ritz-Galerkin method. The prominent advantages of the out-ridged waveguide over the existing waveguide structures used in gyrotrons include the simplicity in manufacture, freedom from local modes, good separation of lower order modes, high power handling ability, and good beam-field coupling at higher harmonics of the electron gyrofrequency. Gain-frequency functional curves of the gyrotron traveling wave amplifiers with the out-ridged waveguide and some other waveguide structures are computed numerically by employing the general analytical results developed in [15].     

Smoothly wavelength-tunable picosecond pulse generation using a harmonically mode-locked fiber ring laser

A simple design of a stable, smoothly wavelength-tunable picosecond pulse generator has been demonstrated using a dispersion-tuned, harmonically mode-locked fiber ring laser with a directly modulated semiconductor optical amplifier (SOA). The SOA functions as both a polarization-insensitive mode locker and a supermode noise suppressor. Near-linearly chirped pulses are generated and compressed to less than 4 ps when the intracavity dispersion is anomalous while 11-ps, near-transform-limited pulses are generated without compression when the dispersion is normal. Smooth wavelength tuning is achieved over more than 11 nm by only tuning the modulation frequency and pulse characteristics are stable over the entire tuning span. A simple numerical model successively simulates the operation principle of the system. The tuning range is determined by both the gain profile and the total intracavity dispersion. The dispersion and the SOA ensure the long-term stability of the system.     

Sum-frequency light generation in optical fibres pumped by a Q-switched laser

Sum-frequency light in optical fibres, pumped by a Q-switched laser, was investigated. The 0.54 ?m sum-frequency light, generated from a combination of a 1.064 ?m pump light and the 1.12 ?m first Stokes light, is observed above 80 W input power and found to increase with the square of the input power.     

Pulse saturation in a traveling wave parametric amplifier

The pulse saturation on a nondispersive traveling wave parametric amplifier is solved in the slowly varying approximation with space and time by reducing the dynamic equations to a degenerate form-of the sine-Gordon equation. If the group velocity of the signal wave differs from that of the pump and idler waves, the signal wave obeys the sine-Gordon equation.     

Bandwidth-limited picosecond pulse generation by hybrid mode-locking in a ring cavity GaAlAs laser

Bandwidth-limited picosecond pulses have been obtained using hybrid active/passive mode-locking in an external cavity semiconductor diode ring laser. Active mode-locking by application of sinusoidal RF modulation at the cavity round-trip frequency to a diode laser providing gain is supplemented by passive mode-locking in a second laser which is biased to provide saturable loss. Simultaneous streak camera and scanning Fabry-Perot interferometer measurements show that bandwidth-limited pulses of 25 Ps duration are obtained. Operation is not limited to near laser threshold, and frequency detuning sensitivity is improved when compared to the case of purely active mode-locking.     

Q-switched pulse generation with lutetium oxide absorber

A lutetium oxide (Lu2O3) film was proposed and demonstrated for Q-switching operation at 1.55 µm region. It was obtained by solving Lu2O3 powder into isopropyl alcohol and mixing the solution into polyvinyl alcohol (PVA) solution to form a composite precursor solution via stirring, sonicating, and centrifuging processes. The thin film was formed through a drop and dry process and a small piece of this film was integrated into erbium-doped fiber laser (EDFL) cavity to modulate the cavity loss via Q-switching mechanism for pulse generation. The Q-switched laser operated at 1 565 nm with the repetition rate of 75.26 kHz as the pump power was raised to the maximum value of 145.83 mW. The maximum pulse energy of 41.85 nJ was recorded at 145.83 mW pump power. The mode-locked pulse operated at 968.5 kHz with a pulse width of 510 ns was also realized in an extended EDFL cavity. The simple and cost-effective laser should have various applications including material processing, sensing and biomedical areas.     

Picosecond optical pulse generation from mode-locked phased laser diode array

Actively mode-locked 26 ps optical pulses are generated from a gain-guided, 10-stripe, phased laser GaAs diode array with an external cavity consisting of two cylindrical lenses and a corner reflector. To our knowledge, this is the shortest pulse width yet demonstrated from a mode-locked phased laser diode array. The detuning bandwidth of the mode-locking is measured as 2.5 MHz.<>     

High-repetition-rate optical pulse generation using a rationalharmonic mode-locked fiber laser

Rational harmonic mode locking takes place in an actively mode-locked fiber laser when the modulation frequency f_m=(n+1/p)f_c, where n and p are both integers and f_c is the inverse of the cavity round-trip time, the 22nd order of rational harmonic mode locking has been observed when f_m ≈1 GHz. An optical pulse train with a repetition rate of 40 GHz has been obtained using a modulation frequency f_m=10 GHz. The theory of rational harmonic mode locking has also been developed. The stability of the mode-locked pulses is improved considerably when a semiconductor optical amplifier is incorporated into the fiber laser cavity. The supermode noise in the RF spectrum of a mode-locked laser is removed for a certain range of current in the semiconductor optical amplifier     

All-optical phase modulation in a traveling wave semiconductorlaser amplifier

A novel all-optical phase modulation and wavelength conversion has been demonstrated in a traveling wave semiconductor laser amplifier. Even though the optical gain modulation caused by the saturation effect in a traveling wave semiconductor laser amplifier is sensitive to the signal wavelength, the optically controlled phase modulation is relatively independent of the signal wavelength     

Generation of high-power picosecond pulses from a gain-switched two-section quantum-well laser with a laterally tapered energy-storing section

We investigated experimentally the potential of generating high power gain-switched pulses from a two-section laser diode containing a laterally tapered energy-storing section and a ridge-waveguide modulation section. In particular, picosecond pulses with energies above 20 pJ and peak powers about 1 W were obtained by electrical pulse modulation at a repetition rate of 250 MHz. Large-signal operation up to the GHz range was also demonstrated. The lateral far-field pattern exhibited a single lobe subtending an angle near the diffraction limit, which showed that the lateral mode was well-controlled by the ridge-waveguide section.