QD lasers have a very low threshold current densities of range _______

1.	QD lasers have a very low threshold current densities of range __________
A.	0.5 to 5 A cm<sup>-2</sup>
B.	2 to 10 A cm<sup>-2</sup>
C.	10 to 30 A cm<sup>-2</sup>
D.	6 to 20 A cm<sup>-2</sup>
Answer» E.

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