Fig.1. (a) Two-dimensional photonic crystal etched through a vertically monomode semiconductor InP-based heterostructure ; (b) Dispersion relations of the W3 waveguide folded into the first Brillouin zone; (c) Micrograph of a three-missing-rows PCCW (top view) with period a=400 nm in a InP heterostructure containing quantum wells.

Fig. 2. (a) Scheme of the setup with two pump beams (Cam=camera; Sp=Spectrometer; Fib=optical fiber; BS=beamsplitter; P=polarizer; MO=mirror objective; S=sample; LO=lens objective; F1 to F4=filters, L=lens; CL=cylindrical lens; P=probe laser diode; G=gain laser diode); (b) scheme of the sample and excited areas for gain measurement in an unpatterned region (left) and in a PCCW (right); (c) principle of the gain soustraction method.

Fig. 3. (a) Bare spectra for the unpatterned measurement region, as indicated in Fig. 2(c), so that n I_pg (top spectrum), I_g was already subtracted ; (b) Gain difference spectrum from the above measurements, with a comparison to the expectation from basic gain theory with quantum well square-shaped joint DOS ; (c) Gain difference spectra for the three-missing-row 60a-long photonic crystal waveguide. The dip is the mini-stopband region. Note the two peaks on each side; (d) Plot of the group index n_g=c(∂k/∂ω) of the fundamental mode as a function of wavelength, calculated by using the plane wave expansion method, and negative for consistency with Fig. 1(b). Note the divergence of n_g at the edges of the mini-stop-band.