Simultaneous multiple-wavelength operation of a multistripe array grating integrated cavity laser is reported. We demonstrate simultaneous lasing from a single output port at 2, 3, and 4 discrete wavelengths, each independently selected from a comb of 9 wavelengths set at -2 nm intervals, from 1512 to 1.528 nm. Signal cross talk is examined for the case of two-wavelength emission and found to be independent of the wavelength separation. The emission wavelengths were linearly spaced to within

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... .02 nm, while the comb's central wavelength deviated by less than 2 nm from its design value. This is the highest wavelength linearity and accuracy so far recorded for a monolithic multiwavelength source. Wavelength division multiplexing (WDM) is being nar waveguide. The operation of the MAGIC laser resemwidely considered for use in future fiber networks by both bles that of a bulk-optic external cavity laser, for which the the telecommunications and computer industries. ' Many single laser element and rotating grating of the latter have of the proposed networks call for multiple-wavelength been replaced by an array of laser stripes and a fixed etched sources at the-access points (and nodes) within the netgrating, the etched grating being curved to provide focuswork. System integrity requires that all such sources proing as well as diffraction. The MAGIC laser is shown schevide signals at the same precisely defined wavelengths. matically in Fig. 1 . Banks of independent distributed feedback (DFB) lasers have already been used in WDM network demonstrations, their different wavelength outputs being combined in an external bulk-optic multiplexer to form a single multiwavelength source.2-4 Integration of these separate lasers on a single chip potentially offers great advantage through reduced component count and packaging costs, as well as through improved reliability.5c However, integration removes the ability to independently temperature tune the wavelengths of the individual laser elements. Very precise control of the 'growth and fabrication of each element is therefore necessary in order to accurately set all wavelengths. We have recently reported a new type of semiconductor laser source, the multistripe array grating integrated cavity (MAGIC) laser?z8 We have already demonstrated single-wavelength operation of this device, showing that lasing can occur at a wavelength selected from a predetermined comb of values. 778 In this letter we report the first demonstration of simultaneous multiwavelength operation of a MAGIC laser. Simultaneous operation at 2, 3, and 4 wavelengths is reported, each wavelength being independently selected from a comb of 9 wavelengths spaced at -2 nm intervals across the spectral range of 1512-1528 nm. The multiple-wavelength emission occurs from a single output port. Record precision of wavelength positioning is also demonstrated. Finally, we examine signal cross talk for the case of two-wavelength operation and show that it is approximately independent of the wavelength spacing. If a single active stripe of the MAGIC laser is electrically pumped, laser emission occurs from its cleaved end facet at a wavelength determined by the optical feedback from the grating. The lasing wavelength is different for each stripe, being defined by the stripe's position relative to the grating.' Laser emission at different wavelengths from a singie output port is also possible. An "output" stripe toward one end of the array is selected and pumped, and a Ysecond" stripe toward the opposite end of the array is also pumped. If the two stripes are chosen such that the direct grating-feedback wavelengths for each occur at opposite extremes of the active material gain spectrum, then the wavelength at which the grating "connects" the two lies toward the middle of this spectrum, and so lasing occurs preferentially at the connecting wave1ength.s By then, pumping different second stripes, the emission from the output stripe may be switched from one wavelength to another. In this letter, we report the simultaneous operation of the MAGIC laser at a number of different wavelengths, achieved by simultaneously injection pumping a number of different second stripes together with the single output stripe. Each emission wavelength is determined by the resonance between the output stripe and one second A MAGIC laser is formed by the monolithic integration of an active stripe array with a diffraction grating, the latter being etched into one end of a two-dimensional pla-output L*%--R-1 (b-1 Planar Waveguide "%sitor from Department of Physics, University of Surrey, UK. FIG. 1. Sketch of the MAGIC laser. Shaded stripes illustrate those injection pumped for simultaneous multiwavelength operation; laser emission is collected from the common output stripe. grating