The invention relates to systems and methods for improving optical detection and sensitivity in situations in which emission of luminescent light is monitored. It is provided a sample carrier which achieves increased sensitivity of luminescent light detection. The sample carrier comprises a sample carrying part and a light reflecting part; wherein the light reflecting part is positioned to allow an optical collection and detection system to collect not only luminescent light emitted from the sample positioned on the sample carrying part in a direction of the optical collection and detection system, but also luminescent light emitted from the sample in a direction away from the optical collection and detection system and reflected in the direction of the optical collection and detection system via the light reflecting part. When an excitation light source is needed, the light reflecting part also allows the excitation light rays passing through the sample to hit the light reflecting part, and reflect back in the opposite direction thus the reflected excitation light also passes through the sample. Also provided are methods of using such a sample carrier.