High-power (more than 500 mW) and high-speed (more than 1 Gbps) tapered lasers at 1060 nm are required in freespace
optical communications and (at lower frequencies of around 100 MHz) display applications for frequency
doubling to the green. On a 3 mm long tapered laser, we have obtained an open eye diagram at 1 Gbps, together with a
high extinction ratio of 11 dB, an optical modulation amplitude of 530 mW, and a high modulation efficiency of 13
W/A. On a 4 mm-long tapered laser, we have obtained an open eye diagram at 700 Mbps, together with a high
extinction ratio of 19 dB, a high optical modulation amplitude of 1.6 W, and a very high modulation efficiency of
19 W/A. On a 6 mm-long tapered laser, we have obtained a very high power of 5W CW and a very high static
modulation efficiency of 59.8 W/A.
High-power (more than 500 mW) and high-speed (more than 1 Gbps) tapered lasers at 1060 nm are required in freespace
optical communications and (at lower frequencies of around 100 MHz) display applications for frequency
doubling to the green. On a 4 mm-long tapered laser, we have obtained an open eye diagram at 700 Mbps, together with
a high extinction ratio of 19 dB, a high optical modulation amplitude of 1.6 W, and a very high modulation efficiency of
19 W/A. On a 3 mm long tapered laser, we have obtained an open eye diagram at 1 Gbps, together with a high
extinction ratio of 11 dB, an optical modulation amplitude of 530 mW, and a high modulation efficiency of 13 W/A.
High-brightness diode lasers at 1060 nm are useful in display applications (to provide green light by frequency doubling)
and in free-space optical communications. On Al-free active region laser structures, we have obtained low optical losses
of 0.9 cm-1, a high internal quantum efficiency of 98% and a low transparency current density of 64 A/cm2. On uncoated
broad-area lasers (2 mm x 100 μm) at 20°C CW, we have obtained a high maximum wall-plug efficiency of 66%, and an
optical power higher than 3W per facet.
Based on these good results, we have realized 3.7 mm long gain-guided tapered lasers, delivering a high power of 3W at
10°C CW, together with a low M2 of 3 at 1/e2 and a high maximum wall-plug efficiency of 57%.
We have also realized separate electrode lasers, in which the ridge and tapered sections are biased separately. In this
configuration, the current through the ridge section is only a few tens mA while the current on the tapered section is
several Amps. This allows to control a large output power with only a small change of the ridge current. By moving the
ridge current from 0 to 50 mA, keeping a constant 4A current through the tapered section, we have obtained a large
change of the output power from 0.09 W to 2.6 W, which corresponds to a high modulation efficiency of 50 W/A under
static operation. In dynamic regime, the separate electrode laser can be operated at 700 Mbps, showing a high
modulation efficiency of 19 W/A, optical modulation amplitude of 1.6 W and extinction ratio of 19dB [1]. These
modulation efficiencies are, to our knowledge, record values.
The Shannon capacity limit of multimode fibers with asymmetric impulse responses is calculated for a 220 m link with a
10GBASE-LRM standard link power budget. Results show that a 1:2 asymmetric Bi-mode case allows largely
bandwidth independent behavior near the maximum Shannon capacity.
We report a compact transmitter with 0.4 W output optical modulation amplitude at 1 Gb/s using a twin-contact directly
modulated laser with a ~100 mA applied current swing and a 2 A constant bias current. Bit-error-ratio measurements
confirm high signal quality for optical wireless communication applications.
We study the transmission performance of Manchester encoded signals over multimode fibers at 1.25 Gb/s and 2.5 Gb/s
focusing on regimes where there is strong slowly time varying signal fading and noise corruption. This fading and noise
is due both to the modal noise and the dispersion varying cruel environmental effects. A non-return-to-zero (NRZ)
modulation scheme typically used in the transmission suffers severally from such slowly varying signal fading; whereas
Manchester encoded signal, which carries the binary value by the pulse position within a bit slot, in contrast, has a better
performance in coping with the slowly varying signal degradation. In this paper, we study the transmission performance
of these two signaling schemes, and the results show that Manchester encoding outperforms NRZ in coping with slowly
varying signal degradation.
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