Overlapping wavelength-tunable vertical cavity surface-emitting laser (VCSEL) arrays

A monolithic vertical-cavity surface-emitting laser (VCSEL) array comprising a plurality of tunable VCSELs, each VCSEL having:

• (a) a first reflector and a second reflector positioned so as to define a laser cavity therebetween;
• and
• (b) a semiconductor active region disposed between the first and second reflectors, the active region comprising a material characterized by a gain spectrum and capable of amplifying light at wavelengths within a tuning range, each VCSEL of the plurality of VCSELs having substantially identical active regions with substantially identical gain spectrums;
• wherein all, or all but one, of said VCSELs, further comprise:
• (c) a phase-shift layer disposed in the laser cavity between the active region and the second reflector, the phase-shift layer for each VCSEL having a unique thickness, wherein:
• up to one VCSEL of the plurality of VCSELs may have no phase-shift layer, said one VCSEL being considered to have a zero phase-shift layer thickness;
• each VCSEL of the plurality of VCSELs has a unique effective optical cavity length corresponding to said VCSEL's unique phase-shift layer thickness;
• and
• each VCSEL is capable of generating laser light at a selected lasing wavelength within the VCSEL's tuning range, for a given gain spectrum and unique effective optical cavity length, by applying a corresponding tuning condition to the VCSEL, wherein the unique effective optical cavity lengths of the VCSELs of the plurality of VCSELs are selected so that (1) under identical tuning conditions, each VCSEL of the plurality of VCSELs generates laser light at different lasing wavelengths;
• and (2) the tuning range of each VCSEL overlaps with the tuning range of at least one other VCSEL so that each VCSEL is capable of generating laser light at a selected lasing wavelength lying within the tuning range of the at least one other VCSEL.