Five-wavelength integrated DFB laser arrays with quarter-wave-shifted structures

Spatial hole burning effects in distributed feedback lasers

“…The effects of spatial hole burning on multimode effects in DFB lasers have been studied and found to be very strong for index coupled modes and weak for gain coupled modes. The analysis indicates, in agreement with some experimental results found by others [17], [19], [20], that index coupled DFB lasers may lose SLM behavior as their output power exceeds a few times the saturation power of the medium. Thus, it would seem advantageous to use gain coupled DFB lasers for work that requires a narrow linewidth much above threshold.…”

“…For index coupling greater than about 0.5 or modulation strength parameters greater than 0.2, the approximate gain solution represented by (20) is in close agreement with the exact numerical solution of the DFB coupled mode equations including spatial hole burning. The use of the approximate solution represents a considerable savings in computer time, often reducing the amount of time necessary to calculate a solution by more than an order of magnitude.…”

“…If we now use (18a) and (18b) in the LHS of (15) and (16a) and (16b) in the RHS of (15) and cancel the common factor of A, we find with some additional manipulation where C = sinh yL( + i) (sinh y L ( -;))* For the case of bulk modulation (gain 'coupling), m # 0, K = 0, we proceed somewhat differently. Starting from (15), we replace the LHS with the values of R,,, and Sou, as determined by (1 6a) and (1 6b) in the RHS of (15) and factoring out the common term of A , we find Equations (19) and (20) can be solved using a relatively simple numerical integration, and similar equations for the mode detuning 6 can be found, but as we will show in the next section, 6 changes relatively little from its threshold value when the DFB laser is operated above threshold.…”

“…We were then able to increment the power by larger values while still providing the good guesses of the free parameters needed for the shooting method to converge. The approximate gain equation (20) was solved by Romberg numerical integration for the same range of powers as the exact equations. All the numerical work was done in Fortran on a Macintosh I1 computer.…”

The Fabrication of Laser Array by Holographic Interference Lithography

“…This is usually realized by e-beam lithography [2], which is an expensive and low throughput fabrication technique. Use of holographic interference lithography can be realizable [3].…”