Fig. 1. Energy band diagram of an ICL active stage i composed of an InAs/Ga_0.7In_0.3Sb/InAs W-type active QW sandwiched by an InAs/AlSb chirped superlattice electron injector on the left side and a GaSb/AlSb double QW hole injector on the right side. Calculated probability density functions are shown for the upper and lower lasing subbands E_{e_i} and E_{h_i}, the hole injection level E_{hj_i}, and the electron injection miniband, where the lowest electron injection level is E_{ej_i}. Four InAs QWs in the electron injector of stage i + 1 are also shown on the right side to illustrate the SMIF for carrier transfer between two sequent stages. The layer structure of the active stage i from the left is as follows: 2.5 nm AlSb/3.0 nm InAs/1.2 nm AlSb/2.7 nm InAs/1.2 nm AlSb/2.4 nm InAs/1.2 nm AlSb/2.0 nm InAs/1.2 nm AlSb/1.8 nm InAs/1.1 nm AlSb/1.7 nm InAs/2.5 nm AlSb/1.7 nm InAs/3.0 nm Ga_0.7In_0.3Sb/1.4 nm InAs/1.0 nm AlSb/3.0 nm GaSb/1.0 nm AlSb/4.5 nm GaSb/2.5 nm AlSb. Four underlined InAs electron injector QWs were doped with Si to 2 × 10¹⁸ cm^-3. The bulk conduction band (CB) edge and valence band (VB) edge are indicated by the dark blue and purple lines, respectively.

Fig. 2. (a) High-resolution XRD pattern measured around GaSb (004) (top) of the epitaxial complete device structure and the dynamic simulation of the same structure (bottom); (b) AFM image measured on the surface of a complete device structure.

Fig. 3. Lasing spectra of the ICL at various temperatures.

Fig. 4. (a) Measured inverse of the external quantum efficiency 1/η_ext as a function of cavity length L and (b) threshold current density J_th as a function of the reciprocal of cavity length 1/L. Values of internal quantum efficiency, internal loss, peak modal differential gain, and transparency current density are obtained by fitting the data with Eqs. (1) and (2).

Fig. 5. CW L-I-V characteristics for a 15-µm-wide, 5-mm-long device with HR and AR coating at various heat-sink temperatures between 10°C and 60°C.

Fig. 6. (a) CW threshold current densities and (b) differential slope efficiencies versus temperature for an HR/AR and an UN/UN samples.

Fig. 7. (a) CW output power of a 15 µm × 3 mm ICL. The data were recorded every hour. (b) L-I-V characteristics for the ICL measured before the lifetime test (0 h) and after CW operation for 3500 h, 3900 h, 4700 h, and 6400 h.