Laser emission using photonic crystal microcavities (PCM) [1] has opened new ways towards very low threshold and highly efficient solid state lasers with also very small size [2,3]. Recently, the term "thresholdless" has been used in the literature [4] to identify lasers presenting two main features: a spontaneous emission coupling factor (β ) close to 1 and low non radiative losses. Non radiative losses are reduced by several orders of magnitude at cryogenic temperatures, although they can never be completely suppressed. When the spontaneous emission factor β is equal to 1 every photon emitted by the device is emitted in the lasing mode. Such "thresholdless" lasers were proposed by Noda [4] to be realized by combining QDs as light emitters and PCMs as high quality resonators. Using that recipe, ultra-low threshold lasing has been achieved at cryogenic temperatures using an ever-decreasing number of QDs within PCMs. [2,[5][6][7] That strategy was adopted by Strauf et al. to demonstrate near thresholdless lasing at low temperature (4.5 K) by using few QDs (between 2 to 4) as active emitters and a high β =0.85 with power theshold values of 124 nW.[5] Khajavikhan et al. recently demonstrated thresholdless operation at low temperature (4 K) using metallic microcavities instead PCMs. [8] In this work we report a RT continuous wave (c.w.) laser with emission characteristics close to those of an deal thresholdless laser. [6]

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