**3. Optical measurement system and the foundatment mode of PhC laser**

Section 3.1, the angular-resolved μ-PL (AR μ-PL) system will be introduced, including the pumping lasers, light paths, and so on. Then, using the AR μ-PL system, the characteristics of foundament mode PhC laser would be shown in Section 3.2 and 3.3, such as threshold characteristics and far field patterns, etc. Furthermore, by adopting the multiply scattering method (MSM), the threshold gains of foundamental modes PhC lasers can be calculated in Section 3.4.
