Search

Novel 4-chlorophenylhydrazono-3-oxo-1,2,3,4-tetrahydropyridazino[3,4-b]quinoxalines 10a-c were synthesized by the cyclization of the α-hydrazonohydrazides 8a-c. The chlorination of 10a with phosphoryl chloride afforded 3-chloro-4-[2-(o-chlorophenyl)hydrazino]pyridazino[3,4-b]quinoxaline 12.

This paper describes an improved method for the synthesis of 3-(3-chloroquinoxalin-2-yl)-1,2-dihydro-1-formyl-2-oxo-3H-1,5-benzodiazepine (2) and its conversions into novel 3-substituted 1,5-benzodiazepine derivatives (3a,b and 4a,b).

The reaction of 3-(2,3-dihydro-4-methyl-3-thioxo-4H-1,2,4-triazol-5-ylmethylene)-2-oxo-1,2,3,4-tetrahydroquinoxaline 4 with o-chlorobenzenediazonium chloride gave 3-[α-(o-chlorophenylhydrazono)-2,3-dihydro-4-methyl-3-thioxo-4H-1,2,4-triazol-5-ylmethyl]-2-oxo-1,2-dihydroquinoxaline 6, whose refluxing in phosphoryl chloride/pyridine afforded 1-(o-chlorophenyl)-3-(2,3-dihydro-4-methyl-3-thioxo-4H-1,2,4-triazol-5-yl)-1H-pyrazolo[3,4-b]quinoxaline 7. The reactions of 6 and 7 with nitrous acid resulted in sulfur extrusion to provide 1-(o-chlorophenyl)-3-(4-methyl-4H-1,2,4-triazol-5-yl)1H-pyrazolo[3,4-b]quinoxaline 8 and 3-[α-(o-chlorophenylhydrazono)-4-methyl-4H-1,2,4-triazol-5-ylraethyl]-2-oxo-1,2-dihydroquinoxaline 9, respectively.

An ultrafast time-domain optical multi/demultiplexer utilising the optical Kerr effect in two birefringent fibres concatenated with each fast axis crossed is proposed. Stable demultiplexing of an ultrashort 30 ps optical pulse train at 1.97 GHz from a gain-switched DFB LD has been successfully demonstrated using CW mode-locked Nd:YAG laser control pulses.

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.

The first demonstration to compress the linearly chirped optical pulses from a gain-switched distributed-feedback laser diode (DFB-LD) is described at 1.3 μm wavelength. By travelling through a highly dispersive single-mode fibre with 48 ps/nm normal dispersion, a 26 ps (FWHM) pulse having red-shift frequency chirping of 85 GHz (FWHM) is compressed to 8.3 ps with the time-bandwidth product of 0.71.

The reaction of N-(1, 2-bisethoxycarbonylvinyl)-o-aminoacetophenone (IVc) with an excess of hydrazines or guanidines gave 4-hydroxy-1-oxo-1, 2-dihydropyridazino [4, 5-b]-quinolines (Ia, b) or 1, 3-dioxo-1, 3-dihydropyrrolo [3, 4-b] quinolines (IIIc, d), respectively. It was found that 2, 3-bishydrazinocarbonyl-4-methylquinolines (VIa, b) were converted to 4-hydroxy-1-oxo-1, 2-dihydropyridazino [4, 5-b] quinolines (Ia, b) and 1, 3-dioxo-1, 3-dihydropyrrolo [3, 4-b] quinolines (IIIa, b) under different reaction conditions.

No-chirped high-peak-power optical pulses at a 2.6 GHz repetition rate from gain-switched 1.3 mu m distributed feedback laser diodes were obtained using both linear fibre compression, and Raman amplification. Coupling these pulses into a dispersion-shifted single-mode optical fibre, the authors have demonstrated optical soliton propagation at a high repetition rate using the laser diodes.

Optical soliton propagation at a 3 GHz repetition rate is demonstrated using optical pulses from a gain-switched 1.55 mu m distributed feedback laser diode. An Er/sup 3+/-doped fibre amplifier and a Raman amplifier, both pumped by 1.47 mu m Fabry-Perot laser diodes, are employed for achieving high-peak-power optical pulses and fibre-loss compensation, respectively.

An all-optical spatial time-division multiplexer is demonstrated using fibre-type 2 × 2 couplers and fibre delay lines. 100Gbit/s modulated optical signals are successfully generated by 32-times multiplication of 3.125Gbit/s, 6ps compressed pulses, from a gain-switched DFB laser diode.

12 GHz chirped optical pulses from a gain-switched 1.3 μm distributed feedback laser diode are compressed to transform-limited 5.6 ps pulses by travelling through a dispersion shifted single-mode fibre with 46 ps/nm normal dispersion. A time-bandwidth product of 0.69 and a high on/off ratio of 20 dB are obtained for optimally compressed pulses.