I assume that you wanted to ask about the 1st millennium CE. More specifically, you might even want answers to address its second half, between c. 500 and c. 1000. There is certainly a case for placing technical innovations in this period. /u/Ambarenya, for instance, submitted in this post a list of Byzantine achievements, some of which can be called technological developments. Others could be found in the West. However, I think that this is partly missing the point. For a start, the 'Dark Ages' are not called like that because of their technological backwardness, but rather because of an image of crumbling civilisation and poor documentation (the first one being, of course, a caricature; the second one can only be endorsed in certain regions, during certain periods).

In general, until the start of the Modern era, or even of the 19th century, it is ill-guided to think about a period in terms of technological development. Technical progress was slow and haphazard; great periods of time (often centuries) separated an invention and its diffusion within a single region. It does not mean that we cannot try to assess local technological levels at a given time. For instance, it is indeed possible to say that the loss of the potter's wheel in post-Roman Britain, a clear technological regression, shows the gravity of the social collapse in the 5th century. But looking at the Early Middle Ages as a whole, it cannot be said to be a particularly poor, nor indeed particularly brilliant period for innovation. And the same thing can be said about approximately any given period of five centuries over the course of human history until 1700/1800.

Rather, what we consider to be important breakthroughs were achieved through human organisation. The overall technical level of, say, southern Gaul in 100 and 700 CE would not be very far away from each other; but their levels of social and political organisation were indeed quite different. Conversely, the heavy plough, often showcased as the early medieval invention that transformed Europe in a breadbasket, seemingly existed for some time without being adopted on a large scale; it is only new patterns of organisation and settlement that transformed it into a game-changing invention.

To take /u/GeorgiusFlorentius's answer in a different direction, part of the reason why many historians avoid the term "Dark Ages" is because it's a profoundly euro-centric view. He mentions that technological progress ought not to be our yardstick, but even it was, the rest of the world was getting along just fine in the "European Dark Ages" spreading paper throughout Asia, inventing movable type, early forms of gunpowder, algebra and other mathematical advancements, the advent of the translation movement, etc. etc.