In this paper we experimentally demonstrate dual-carrier modulation scheme to achieve spectrally efficient OFDM transmission in an optical wireless communication link using a hybrid laser-LED transmitter. The hybrid transmitter used in this work consists of two near infrared laser diodes at 785 nm and 808 nm used to separately modulate the real and imaginary components of the complex OFDM waveforms, collinearly combined and subsequently mixed with white LED array at a diffuser surface for indoor illumination. At the receiver end, two separate high-speed photodetectors with spectral filters are used to detect the real and imaginary components and subsequently combined to generate the complex OFDM waveforms. The optical system performance is characterized to quantify the beam spread, spot-size and spectral content of the laser beams and white LED array. The communication performance is also characterized using 16, 32, and 64-QAM/OFDM with 1, 1.25 and 1.5 Giga-samples/second sampling rates. The best communication performance with a net data-rate of 4.2 Gbps for 64-QAM/OFDM at an optimum sampling rate of 1.5 G-Samples/second is demonstrated. The dual-carrier modulation scheme studied in this work helps achieve improved spectral efficiency for OFDM transmission in an OWC link using dual transmitter-receiver pair, while at the same time requiring simplified electronic front-ends and encoding/decoding algorithms.